Global powers have been pressing Saleh to sign a Gulf-mediated deal to hand over power to stem spreading chaos in Yemen, a haven for al Qaeda militants and neighbor to the world's biggest oil exporter, Saudi Arabia. The turmoil was a factor in keeping up oil prices on Tuesday, traders said.

 "The ceasefire agreement has ended," a government official said, adding that tribesmen had seized a state building.

 On May 31, there were three main flashpoints in the troubled country - fighting in the capital, government troops gunning down protesters in Taiz in the south and a battle with al Qaeda and Islamic militants in the coastal city of Zinjibar.

UN human rights chief Navi Pillay said 50 people may have been killed by government forces since Sunday in Taiz.

Explosions rocked a northern district of Sanaa on May 31 that houses the headquarters of an army division headed by Ali Mohsen, an influential general who has joined the opposition.