Fighting has again broken out in the Yemeni capital, Sana between tribal groups and forces loyal to President Ali Abdullah Saleh. Reports said the clashes erupted this morning breaking down the truce. Yemeni forces killed more than 20 opposition demonstrators yesterday in the southern city of Taiz. Republican Guard troops and plainclothes gunmen backed by tanks moved in before dawn, opening fire on crowds in the city's main square where protesters had been camping for weeks. Meanwhile, government warplanes launched airstrikes on the town of Zinjibar, which was seized by Islamist militants a day earlier. Yemeni officials said at least four soldiers have been killed in Zinjibar, raising the city's death toll to more than 30.