Tens of thousands of Yemenis displaced by warfare between the government and Shiite rebels are stranded around the war zone with aid agencies unable to reach them because of the intensified fighting, U.N. officials and rights activists said.

The humanitarian crisis has been worsened by tribes in the region robbing relief convoys as well as heavy rains that have washed away tents in some camps, they said.

Yehia Abdel-Wahab, a 46-year old farmer, told The Associated Press on Thursday that his family and 16 others were living in the open after fleeing the fighting in northern Yemen.

"We are living on handouts from the locals," he said by telephone, saying he, his mother and his three children have been living for days under a tree in the Batna region about 60 miles north of San'a and that no aid has reached the area.

"It is getting cold and we are missing many things," he said. "We are suffering from neglect. We are only getting promises made of air."

Abdel-Wahab fled his home in the region of Horf Sufyan further north. He stopped first at a makeshift camp nearby, but then fled further south because the fighting was spreading. Two days after he left the makeshift camp, it was hit by government warplanes in a strike that killed nearly 80 people.

Fighting has dramatically escalated since August between government forces and the rebels, causing turmoil in a nearly 160-mile, mountainous stretch between Yemen's capital San'a and the Saudi border. Even before the current escalation, the fighting had displaced some 150,000 people since it began in 2004.

Since August, tens of thousands more have been forced to flee their homes, but exact numbers are unclear, a reflection of the chaos. Government officials put the number at around 60,000, while the international aid agency OXFAM estimates them at 100,000.

The U.N. refugee agency and International Red Cross say they have about 37,000 newly displaced people who have been registered and are receiving assistance, many in camps around the north.

Thousands more are stranded around the area, some living along roadsides, some trapped in Saada — the home of the rebels, which has been at the center of fighting. Two cease-fires declared by the government in the past month fell apart within hours.

Up to 30,000 are trapped north of Saada near the Saudi border, said Laure Chedraoui, a spokeswoman for the U.N. refugee agency said. The UNHCR has appealed to Saudi Arabia and Yemen to let relief supplies across its border to reach them but has yet to get permission, she said.

Furthermore, old camps that were holding those who fled earlier fighting have filled with a new influx and are inaccessible because of the turmoil, she said.

Officials say they are struggling to set up new camps while dealing with declining supplies.

Newly displaced people continue to trickle daily into the established camps in Saada province and the neighboring province of Amran, some walking for days before making it to refuge, Andrej Mahecic, a UNHCR spokesman said in Geneva on Tuesday.

Tents in one camp housing 5,000 people in neighboring Hajjah province were damaged by heavy rains, leaving hundreds of families without shelter, Mahecic said.

Human rights activist Mahmoud Taha said the authorities and international aid agencies failed to set up a new camp in the Amran area to absorb the stream of fleeing civilians because a local tribe refused to give the land for the camp without charging a fee.

Taha, an Amran resident, said some tribes are also robbing aid convoys — taking at least seven trucks of supplies.

The rebellion started in 2004 when Shiite fighters took up arms against the central government complaining of neglect, and widening influence of hard-line Sunni fundamentalists, some of whom consider Shiites as heretics.