Anti-government tribesmen kidnapped the six crew members of a Yemeni military plane Sunday after it made an emergency landing in an eastern desert for technical reasons, military and local sources said.

The aircraft, a Russian-made Antonov-26 twin-engine turboprob, was carrying supplies from Sanaa to Masila oilfields in the east when a technical glitch forced it to land in Hadramawt province, said General Khaled al-Kothairi, who heads a military unit tasked with protecting oil companies.

The pilot, co-pilot, and four soldiers who were on board the aircraft, are safe, he said.

But another military official said that as soon as the jet landed, armed tribesmen captured the crew and a local government official confirmed they were abducted.

"Contacts are underway with the gunmen to secure the release of the crew and allow the army to repair the aircraft and return it to Sanaa," the military official said.

The armed forces have been flying supplies to Masila oilfields five times a week over the past few months, after tribesmen blocked roads in the region to protest against the killing of one of their chiefs.

Supporters of slain tribal chief Said Ben Habrish have vowed to avenge him by preventing authorities from repairing the pipeline that links Masila oilfield to Al-Daba port on the Gulf of Aden.

The move is aimed at depriving the cash-strapped government of Yemen, an impoverished country that relies on oil revenues from a small oil production industry, to shore up its budget.

Tribesmen have blown up pipelines in the restive Hadramawt province and in February they ambushed a military convoy that was escorting technicians on their way to repair a pipeline, killing four soldiers and wounding others.