Supporters of Yemen's former president Ali Abdullah Saleh shout slogans during a rally against Saudi-led coalition airstrikes, in Sanaa April 3, 2015. Violence has been spreading across Yemen since last year, when Iran-backed Shi'ite Houthi fighters seized the capital Sanaa. A Saudi-led coalition has hit the rebels with air strikes over the past week. REUTERS/Mohamed al-Sayaghi