Cease-fire breaks down between Yemeni army, tribes

Heavy fighting resumed Tuesday in Yemen's capital between government troops and followers of the country's most powerful tribal leader, ending a brief cease-fire and again raising the prospect that Yemen's political crisis could veer into civil war.

Government forces attacked the heavily guarded home of Sheik Sadeq al-Ahmar, who heads the most powerful tribal confederation in Yemen and has turned against the embattled president to join the protest movement that has been seeking his ouster since early February.

Al-Ahmar's armed followers fought back and reoccupied several government buildings they had seized in the first round of fighting between the sides last week. There was no immediate information on casualties.

A resident of the capital, Talal Hazza, said an artillery shell exploded outside his home and another destroyed his neighbor's house.

Hazza says the fighting is preventing ambulances from reaching the wounded.

Beyond the capital, violence has erupted in the southern city of Taiz, which has been a hotbed of anti-government protests since the early days of the uprising against President Ali Abdullah Saleh.

Soldiers backed by tanks and bulldozers have moved in to smash a tent camp in a central square in the city and also destroyed a field hospital that had been set up in anticipation of such an attack. A doctor who witnessed the attack said at least 20 people were killed on Monday.

On Tuesday, the U.N.'s human rights office in Geneva said it has received reports from Yemen that more than 50 people have been killed by pro-government forces in Taiz since Sunday. U.N. High Commissioner for Human Rights Navi Pillay cautioned that the reports "remain to be fully verified."

Pillay said in a statement that "such reprehensible acts of violence and indiscriminate attacks on unarmed civilians by armed security officers must stop immediately."