Women sit next to a banner with images of policemen who have been kidnapped, during a protest march in Medellin December 6, 2011. Outraged by the execution of four captives by FARC rebels, tens of thousands of Colombians protested across the nation on Tuesday to demand an end to half a century of guerrilla violence and kidnapping. The banner reads: "Release them!" REUTERS/Albeiro Lopera (COLOMBIA - Tags: CIVIL UNREST MILITARY POLITICS)