SANAA (Reuters) – Yemeni tribesmen said they wrested a military compound from elite troops loyal to President Ali Abdullah Saleh outside the capital Sanaa on Friday as fighting spread, threatening to tip the country into civil war.

Yemeni fighter jets broke the sound barrier as they swooped over Sanaa, where battles between Saleh loyalists and the Hashed tribal alliance led by Sadeq al-Ahmar erupted this week after failure of a deal to ease the president out.

Clashes spread northeast of Sanaa on Friday, where tribes said in addition to seizing a military post in the Nahm region, they were also fighting government troops at two other positions south of the capital.

In Sanaa, tens of thousands of people gathered after Friday prayers for what they branded a “Friday of Peaceful Revolution” against Saleh, releasing white doves and carrying the coffins of about 30 people killed in clashes this week.

Tens of thousands turned out for the rally, inspired by the Egyptian and Tunisian revolutions, though their numbers had dwindled compared to previous weeks after thousands fled Sanaa and the government closed roads around the city to keep out tribes trying to reinforce the Ahmars.

Machinegun fire and sporadic blasts rattled the city before fighting eased after mediation efforts. Ahmar’s fighters evacuated government ministry buildings they had grabbed this week in return for a ceasefire and troops quitting their area.

“We are now in mediation and there has been a ceasefire between the two sides,” Ahmar, close to an Islamist opposition party, told protesters in “Change Square.” “But if Ali Abdullah Saleh returns (to fighting) then we are ready. We are steadfast and victorious.”

“We wanted it (revolution) to be peaceful but Saleh, his sons and his clique wanted war. We will not leave them the opportunity to turn it into a civil war,” Ahmar told Reuters.

But in a sign of hostility between the sides, a government source ridiculed Ahmar for his grandiose statements, saying the state had taught him a “small lesson” and urging him and “his gangs” to turn themselves in to face justice.

Battles this week, the worst since protests began in January, killed around 115 people and let Saleh grab back the initiative, overshadowing the protest movement with the threat of civil war. Yet protesters were determined to see him go.

“We are here to renew our resolve for a peaceful revolution. We reject violence or being dragged into civil war,” said Yahya Abdulla at the anti-Saleh protest camp, where armed vehicles were deployed to protect those praying.

A few kilometres (miles) away, government loyalists staged a short rally, waving Yemeni flags and pictures of Saleh, who has ruled the Arabian Peninsula state for nearly 33 years.

Worries are growing that Yemen, already a safe haven for al Qaeda and on the verge of financial ruin, could become a failed state that would erode regional security and pose a serious risk to neighboring Saudi Arabia, the world’s top oil exporter.

The United States and Saudi Arabia, both targets of foiled attacks by a wing of al Qaeda based in Yemen, are concerned any spread of anarchy could embolden the militant group.

BATTLE AT MILITARY COMPOUND

In Nahm, 100 km (60 miles) northeast of Sanaa, a tribal leader said fierce fighting over three military posts killed 19 and wounded dozens. He said tribesmen had seized one post and were battling for two more as military planes bombed the area.

“There had been some skirmishes between the tribesmen supporting the youth revolution from time to time, but today it became a big armed confrontation,” Sheikh Hamid Asim said.

He had earlier said anti-Saleh fighters killed the commander of the military post they seized. A separate tribal source said the Yemeni air force dropped bombs to prevent the tribesmen from seizing an arms cache there.

The defense ministry blamed the opposition coalition, comprised of Islamists and leftists, for the fighting in Nahm. State television, citing a military source, denied any posts were seized. “These are lies with no basis in truth,” Yemen TV quoted him as saying.

If confirmed, the Republican Guard’s loss of a military post to tribesmen armed with machineguns and rocket-propelled grenades would be an embarrassing setback for Saleh, whose country has become the poorest in the region.

Mediators have been increasingly exasperated with Saleh, saying he had repeatedly imposed new conditions each time a Gulf-led transition agreement was due for signing, mostly recently demanding a public signing ceremony.

Leaders of the G8 leading industrialized nations called on Saleh to step down during a summit in France, but analysts said global powers have little leverage in Yemen, located on a shipping lane through which 3 million barrels of oil pass daily.

FEAR OF CIVIL WAR

Sanaa residents had been streaming out of the capital by the thousands to escape escalating violence in recent days. Others stocked up on essentials and waited in trepidation.

“There is absolute poverty because of this regime. We want change,” said Abdulrahman al-Fawli, 42, an engineer. “But I’m terrified of civil war. I dread this prospect.”

The recent fighting between tribal fighters and loyalists has ignored a commitment to peaceful demonstrations by protesters, many of whom are sceptical about the vested interests of both sides in the armed conflict.

“Saleh and his forces and the al-Ahmar tribe cannot make the civilian state that the protesters want. They stole the limelight of the revolution and undermined it with their fighting,” said Ali Mohammed Subaihy, a doctor.

In the south, dozens of armed men believed to be from al Qaeda stormed into the city of Zinjibar in the flashpoint province of Abyan, chasing out security forces while seizing several government buildings and setting off blasts in others, residents said.

The army had withdrawn from Zinjibar after a battle with militants in March, but later regained control.

Friday’s violence, which killed at least seven people including a civilian, sent hundreds of families fleeing their neighborhoods as shelling continued and warplanes roared overhead. Smoke billowed from a military building.

Similar clashes broke out in Lawdar, also in the south, a government official said.

Saleh has said his removal would be a boon to al Qaeda, but the opposition, which includes the Islamist party Islah, accuses him of exploiting militancy to keep his foreign backing and argues that it would be better placed to fight al Qaeda.

Washington, which long treated Saleh as an ally against al Qaeda, has said it now wants him to go. Saleh’s attempts to stop protests by force have so far killed around 280 people.

(Additional reporting by Mohamed Sudam and Khaled al-Mahdy in Sanaa, Mohammed Mukhashaf in Aden, Erika Solomon in Dubai and from Barbara Lewis in Geneva; Editing by Mark Heinrich and Louise Ireland)