SANAA - Yemeni security forces opened fire on protesters who blockaded a government building on Monday, wounding 10 in a city that has seen some of the largest rallies seeking to oust President Ali Abdullah Saleh, witnesses said. "A large force of police and army attacked protesters and then chased them in residential areas. They opened fire and used tear gas heavily," said Bushra al-Maqtari, an activist in Taiz, south of the capital Sanaa. Thousands of protesters had gathered outside an education ministry building in Taiz on Sunday, many of them teachers and students, demanding the postponement of school exams. Some also chanted anti-Saleh slogans. Two protesters were shot dead on Sunday as security forces tried to break up the demonstration. But the protesters regrouped overnight before security forces moved in with armoured vehicles to disperse them, witnesses said. Many demonstrators across Yemen, who include students, tribesmen and activists, have vowed to stay on the streets until Saleh, who has clung to power despite three months of protests, steps down. About 150 people have been killed in the unrest.