ANAA (Reuters) - Street fighting raged in Yemen's capital on Tuesday ending a tenuous ceasefire between tribal groups and forces loyal to President Ali Abdullah Saleh and edging the impoverished Arab state closer to civil war.
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 neighbour 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 Tuesday, 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.
U.N. 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 Tuesday that houses the headquarters of an army division headed by Ali Mohsen, an influential general who has joined the opposition.
"I think it is the first time missiles are being used in the street battles," a resident said, referring to the loud blasts.
Al Arabiya reported that government forces were bombarding Mohsen's unit, but the Defence Ministry denied it.
State television said tribesmen were again attacking government buildings, some of which they had evacuated under the truce. The report could not be independently verified.
A government spokesman earlier suggested breakaway army units had attacked the ruling party's headquarters in Sanaa.
"What was new in today's clashes is the use of armoured vehicles ... which the Ahmar (tribesmen) don't have," Abdu al-Janadi, a deputy information minister, told Reuters.
Sporadic fighting with tribesmen continued in the nearby Hasaba district, where residents took refuge in basements.
TRUCE BROKE DOWN
Battles in the capital overnight ended a truce between Saleh's forces and tribesmen brokered at the weekend after more than 115 people were killed last week.
Saleh has defied calls from global leaders, elements in his own military and tens of thousands of protesters to end his 33-year-rule, which has brought Yemen close to financial ruin.
He has also exasperated his rich Gulf Arab neighbours by three times agreeing to step down, only to pull out of a power transition plan at the last minute and cling on to power.
The opposition coalition issued a statement calling on Gulf states to withdraw their peace plan and "stand with the Yemeni people and its peaceful revolution".
The breakaway military accused Saleh of starting a civil war and vowed that he and his entourage would be brought to justice.
Mohammed al-Surmi, a doctor at a Sanaa hospital, said two dead and 17 wounded were brought in. The Defence Ministry website said one officer and one civilian were killed, and 13 soldiers were wounded in the fighting with tribesmen.
Full casualty figures were not immediately available due to the intensity of the fighting.
"Three different dynamics are playing out at the same time," said Ginny Hill, who runs the Yemen Forum at the influential Chatham House think-tank in London.
The newest element is the street revolution while the power struggle among the elites and fragmentation of the Arabian Peninsula country have been playing out for some time, she said.
"Saleh's departure could be seen as the beginning of a contested and potentially lengthy process," she said.
TROUBLE IN TAIZ
Saleh's forces fired on hundreds of protesters in Taiz, about 200 km (120 miles) south of the capital, who were trying to gather at the focal point of rallies dubbed "Freedom Square", witnesses and a Reuters cameraman in the city said.
At least three people were killed and scores wounded in the latest fighting there, medical sources said.
U.N.'s Pillay denounced the killings in Taiz wheere troops used bulldozers and bullets to crack down on protesters.
"Such reprehensible acts of violence and indiscriminate attacks on unarmed civilians by armed security officers must stop immediately," Pillay said in an Internet posting.
French Foreign Ministry spokesman Bernard Valero condemned the attacks in Taiz. He also said there was no news on three French aid workers who disappeared in southern Yemen on Saturday. Paris believes they were kidnapped.
Further south, government troops and locals have been trying to oust al Qaeda and Islamist militants from Zinjibar after they seized the town of 20,000 at the weekend.
Residents said bodies were strewn on the streets, the national bank building was burned and explosions rocked the city. Most of the inhabitants have fled.
"Explosions lit the sky," one resident said.
The United States and Saudi Arabia, both targets of attacks by Yemen-based al Qaeda in the Arabian Peninsula, are worried that a spreading state of anarchy is emboldening the group.
Opposition leaders have accused Saleh of deliberately allowing Zinjibar, located near a sea lane where about 3 million barrels of oil pass daily, to fall to al Qaeda to try to show how chaotic Yemen would be without him.
At least 320 people have been killed since protests started about four months ago, inspired by popular uprisings that ended the reign of the long-standing rulers of Tunisia and Egypt.
(Reporting by Mohammed Mukhashaf in Aden, Khaled al-Mahdi in Taiz, John Irish in Paris, Mahmoud Habboush, Nour Merza, and Sara Anabtawi in Dubai; writing by Jon Herskovitz and Firouz Sedarat in Dubai; editing by Mark Heinrich and Lin Noueihed)
