An opposition demonstrator takes off his gas mask to breathe while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

An opposition demonstrator takes off his gas mask to breathe while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

Opposition demonstrators carry Venezuela's flags while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

An opposition demonstrator shows a tear gas grenade while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Christian Veron

An opposition demonstrator walks while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

An opposition demonstrator carries a home made shield that reads "S.O.S liberty" while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

An opposition demonstrator throws a petrol bomb while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

Opposition demonstrators run away while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

An opposition demonstrator clashes with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

Opposition demonstrators run away while clashing with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Marco Bello

Opposition demonstrators clash with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Marco Bello

An opposition demonstrator clashes with riot police during the so called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Marco Bello

Opposition demonstrators wade through Guaire river during clashes with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro, in Caracas, Venezuela, April 19, 2017. REUTERS/Marco Bello

Riot police take position while clashing with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins TPX IMAGES OF THE DAY

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators take down the national flag while clashing with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela, April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Riot police take position while clashing with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Demonstrators rally during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

A demonstrator looks on during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Demonstrators rally during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Demonstrators march during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Christian Veron

Riot police fire tear gas grenades while clashing with opposition demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Riot police take position while clashing with opposition demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Demonstrators take cover during clashes with riot police at the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Demonstrators take cover during clashes with riot police at the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

A demonstrator takes cover as others clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello TPX IMAGES OF THE DAY

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

A demonstrator clashes with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

ATTENTION EDITORS - VISUAL COVERAGE OF SCENES OF INJURY OR DEATH An injured demonstrator is helped during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

An opposition demonstrator blocks the way of an armored car as riot police clashes with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

An opposition demonstrator blocks the way of an armored car as riot police clashes with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

An opposition demonstrator blocks the way of an armored car as riot police clashes with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Riot police take position while clashing with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators march during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Riot police take position while clashing with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Riot police take position while clashing with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Opposition demonstrators walk through the river Guaire during clashes with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Marco Bello

Demonstrators march during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

An injured demonstrator is helped during clashes with riot police at the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Demonstrators clash with riot police during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Riot police clash with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins

Riot police take position while clashing with demonstrators during the so-called "mother of all marches" against Venezuela's President Nicolas Maduro in Caracas, Venezuela April 19, 2017. REUTERS/Carlos Garcia Rawlins