DOWAAN, Yemen — A Yemeni Army unit handed over control of a group of oil fields to a coalition of armed tribes on Friday in an attempt to keep the fields from falling into the hands of Al Qaeda or other militant groups amid the chaos of a continuing bombing campaign led by .
A Qaeda group in the same area seized an army base and its store of weapons on Friday, expanding the group’s .
International aid agencies, meanwhile, said they were growing more worried about a humanitarian catastrophe developing in the country, where the fighting has damaged civilian infrastructure and blocked the provision of essential services.
has descended into a war of all against all: Qaeda fighters, army units loyal to the exiled President Abdu Rabbu Mansour Hadi and separatist tribes in the south are all fighting against one another, and all are fighting the northern alliance between the Houthi religious movement, supported by , and security forces loyal to ’s deposed strongman, Ali Abdullah Saleh.
started its bombing campaign more than two weeks ago, intending to roll back the Houthi-Saleh coalition and help restore Mr. Hadi to power. But that goal has grown increasingly remote. Mr. Hadi has fled the country, the Houthi-Saleh forces have continued to advance, and Al Qaeda’s branch in Yemen has capitalized on the Saudi strikes to extend its own reach.
In Hadhramaut Province around Al Mukalla, the army’s handover of the oil fields to the tribal coalition — essentially for safekeeping — illustrated how the fight is degenerating into a contest among local armed groups filling the void left by the collapse of the Yemeni state.
“We tightened security around the fields and did not allow workers to leave with even a nail,” said Saleh bin Simrat, a spokesman for the coalition, known as the Hadhramaut Tribal Confederacy.
Qaeda fighters have seized the airport, government buildings and a refinery around Al Mukalla, establishing themselves as the most powerful local force. In an effort to win popular support, they have begun calling themselves the Sons of Hadhramaut and have promised to quickly return control of the city to local civilian leaders. When they seized a major army base outside of the city on Friday, they allowed the soldiers inside to leave unharmed, according to a local tribal leader.
Air assaults by the Saudi-led coalition struck Sana, Yemen’s capital, on Thursday night and Friday. People in Sana said the strikes were some of the heaviest to date. According to the United Nations, 18 of Yemen’s 22 provinces have now been hit by airstrikes.
“The conflict is getting higher, and the fighting is increasing,” said Cedric Schweizer, head of the delegation for the International Committee of the Red Cross in Sana. In a telephone briefing for reporters in Geneva, Mr. Schweizer called for a halt to the fighting, so that civilians can safely obtain essential supplies and medical teams can evacuate the wounded.
Food, medicine and fuel are running dangerously low in the country, which is heavily dependent on imports, Mr. Schweizer said. Fuel is needed to generate electric power and keep water systems operating; running out of fuel for hospital generators would be catastrophic, he said.
The United Nations, citing Yemeni Health Ministry reports, said at least 767 people had been killed and more than 2,900 wounded in recent weeks, and Mr. Schweizer said he had heard some estimates of more than 1,000 people killed. Intense fighting has kept medical teams from collecting the dead in some places, he said.
The United Nations, which is already struggling to raise money needed for emergencies in Iraq, South Sudan, Syria and elsewhere, appealed on Friday for nearly $274 million to aid civilians in Yemen.
“Thousands of families have now fled their homes as a result of the fighting,” Johannes van der Klaauw, the United Nations humanitarian coordinator for Yemen, said in a statement. “Ordinary families are struggling.”
The United Nations refugee agency estimated that the most recent fighting had forced nearly 150,000 more people from their homes in Yemen, where about 300,000 were already displaced.
“All the signs are that things are worsening,” said Adrian Edwards, a spokesman for the agency. “Basic services are on the verge of collapse. It’s just getting worse by the day.”