Anti-government protesters shout slogans during a rally to demand the ouster of Yemen's President Ali Abdullah Saleh in Sanaa June 2, 2011. Forces loyal to Saleh battled with tribal fighters in Yemen's capital on Thursday in overnight clashes that killed dozens as a U.S. envoy flew around the region to try and stop a civil war. REUTERS/Ammar Awad (YEMEN - Tags: POLITICS CIVIL UNREST)