SANAA/TAIZ (Reuters) - At least 30 people were killed in Yemen after military jets pounded a southern town held by al Qaeda and troops opened fire on demonstrators demanding an end to President Ali Abdullah Saleh's nearly 33-year rule.
Despite demands by global and regional powers that he step down, Saleh has refused to sign a deal aimed at transferring power and averting a civil war that could destabilize the world's main oil-exporting region.
Global powers are worried that Yemen could turn into a failed state, fears that have been heightened since al Qaeda and other Islamists seized Zinjibar a few days ago.
Three Yemeni soldiers were killed in an ambush near Zinjibar on Monday, a security official said, a day after a similar incident claimed the lives of six troops. Residents said fighter jets strafed militant areas around Zinjibar but also hit buildings in the town of 20,000, killing at least 13 people.
"The city is devastated. All of its residents have left. Even the dogs, animals and donkeys have abandoned it," said an opposition member in the city who asked to be named as Ali.
Medical workers in Taiz said soldiers had opened fire on a demonstration late on Sunday and hit protesters with bulldozers, killing at least 15 and wounding hundreds in what the United States described as an "unprovoked and unjustified attack."
Al Jazeera said in an unsourced report that 57 people had been killed in Taiz over the past two days.
In the capital Sanaa, several explosions and shooting were heard late on Monday in the district of Hasaba, the scene of week-long fighting between Saleh's forces and a rival tribe.
"Sporadic shooting with heavy weapons followed the blasts. But it has stopped now," a Hasaba resident told Reuters.
The clashes, heard for the second night, may have breached a truce between Saleh's forces and the powerful Hashed tribe to stop the bloodiest fighting since unrest erupted in January.
State television later reported new clashes and accused the tribesmen of attacking government forces and buildings using missiles and rocket-propelled grenades. The report could not be independently verified.
At least 300 Yemenis have lost their lives in months of protests inspired by uprisings that toppled the entrenched rulers of Tunisia and Egypt in January and February.
Opposition leaders have accused Saleh of deliberately allowing Zinjibar, on the strategic Gulf of Aden, to fall to al Qaeda in a bid to show how chaotic Yemen would be without him.
The United States and Saudi Arabia, both targets of attacks by Yemen-based al Qaeda in the Arabian Peninsula, are worried that growing chaos in the country is emboldening the group.
The six soldiers were killed and dozens wounded as they were traveling to Zinjibar, a security official and others said.
"Civilians found a military car and an armored vehicle. They were destroyed, and the bodies of six soldiers were found on the roadside," Ayman Mohamed Nasser, editor-in-chief of Attariq, Aden's main opposition paper, said by telephone.
Several hundred al Qaeda and Islamist militants took over the city a few days ago and have been battling locals and government soldiers for control.
Zinjibar residents told Reuters that power and water had been cut off and many civilians were fleeing to nearby towns.
Activists in the southern city of Aden said thousands who fled Zinjibar were being housed in schools, mosques and other public buildings.
A brief calm was shattered late on Sunday when forces loyal to Saleh opened fire on protesters in Taiz, an attack that residents said lasted late into the night.
"Most of the wounded were hit by live bullets, but some were run over by bulldozers," a medical source said from a field hospital in Taiz, about 200 km (120 miles) south of Sanaa.
Security forces arrested dozens of people on Monday to head off plans for another rally in Taiz, where Saleh's troops have burned tents used by demonstrators and parked armored vehicles in a protest area known as "Freedom Square."
The U.S. embassy condemned the attack in Taiz.
"We commend the youth protesters who have shown both resolve and restraint and have made their viewpoint known through non-violent means," the embassy said.
French officials said on Monday it was credible that three aid workers who disappeared in Yemen at the weekend had been kidnapped, although it had still not received any claim of responsibility.
In Yemen, a security official told Reuters a vehicle used by the French aid workers had been found in a remote area outside the town of Saywun, where they had disappeared.
Yemen is the poorest state on the oil-exporting Arabian Peninsula with about 40 percent of its 23 million people living on less than $2 a day.
Additional reporting by Mohammed Ghobari and Mohamed Sudam in Sanaa, Mohammed Mukhashaf in Aden, Mahmoud Habboush, Nour Merza, Sara Anabtawi and Firouz Sedarat in Dubai; writing by Jon Herskovitz in Dubai; editing by Angus MacSwan