Yemeni tribesmen killed a colonel and two of his aides Friday in an ambush on their convoy as security across Yemen collapses during the country's five-month-old uprising against President Ali Abdullah Saleh, security officials said.
Friday's attack happened near Sharab, northwest of the city of Taiz, which has seen huge anti-government protests since the start of the revolt, the officials said, speaking 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.
Yemen's army has been shelling the outskirts of Taiz to try to dislodge the tribesmen. Shells damaged seven civilian homes Friday, injuring two women and two children in one of them, local activists Nouh al-Wafi said.
Also Friday, tens of thousands of protesters took to the streets in cities across the country after Muslim prayers to call for Saleh's ouster after 33 years in power. In the capital Sanaa, thousands also demonstrated in support of the president 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.