Imran Khan(C), the Chairman of the Pakistan Tehreek-e-Insaf (PTI) political party, addresses supporters during the Revolution March in Islamabad August 31, 2014. Thousands of protesters massed outside the residence of Pakistani Prime Minister Nawaz Sharif on Saturday to demand he step down, after efforts to find a negotiated solution to the country's political crisis failed.Pakistan has been gripped by unrest for more than two weeks, with protest leaders Imran Khan and Tahir ul-Qadri saying they will not back back down unless Prime Minister Nawaz Sharif resigns. On Saturday Sharif once again said he would not go. REUTERS/Faisal Mahmood (PAKISTAN - Tags: POLITICS CIVIL UNREST)