At least 10 Yemenis were killed Friday in fighting between government forces and tribesmen seeking to oust President Ali Abdullah Saleh, officials said, raising fears about a collapse of security during a popular uprising in the Arab world's poorest country.
The violence began when armed tribesmen attacked a military convoy, killing a colonel and two of his aides near Sharab, 12 miles (20 kilometers) northwest of Taiz, security officials said. Hours later, the Yemeni army fired tank and artillery shells into Taiz, killing at least seven civilians and wounding more than 30 others, according to medical officials.
Yemen's army has been shelling the outskirts of Taiz, Yemen's second-largest city, to try to dislodge the tribesmen who have joined forces with anti-government protesters.
The officials spoke on condition of anonymity because they were not authorized to brief the media.
The disintegrating security across Yemen has allowed armed tribesmen and radical Islamist groups to take over parts of the country's weakly governed provinces. The U.S. worries that Yemen's active al-Qaida branch will exploit the chaos to step up operations.
Despite the violence, tens of thousands of protesters took to the streets again in Taiz, the capital Sanaa and several other cities after weekly Muslim prayer services to call for Saleh's ouster after 33 years in power, in rallies dubbed "The Friday of a Civic State." Abdullah al-Sami, a Muslim preacher in Taiz, addressed worshippers by saying that the goal of ongoing protests is to establish a new state with equal rights for all citizens.
In Sanaa, thousands of pro-government demonstrators also rallied in a show of support for Saleh outside his palace.
Saleh has been receiving treatment in Saudi Arabia since July 5 after being badly injured in an attack on his palace. Pressure from the U.S. and Yemen's Gulf Arab neighbors has so far failed to get him to transfer power.