Fresh street fighting has raged across the Yemeni capital of Sanaa after a tenuous truce broke down between tribal groups and forces loyal to the president.
Global powers have been pressing Ali Abdullah Saleh to sign a deal to hand over power to try to stem the growing chaos.
An official says the ceasefire agreement brokered at the weekend has ended and tribal groups have gained control of a government building in Sanaa on Tuesday, Reuters reports.
Other flashpoints were in Taiz, where government troops are reported to have gunned down protesters, and Zinjibar, scene of a battle with al Qaeda and Islamic militants.
More than 115 people were killed last week in urban battles with machine guns, mortars and rocket propelled grenades in the bloodiest fighting since anti-government protests began months ago.