Yemeni tribesmen ambushed a military convoy Friday, killed four soldiers and wounding several more, in the restive southeastern province of Hadramawt, a local official said.

The troops were escorting technicians on their way to repair an oil pipeline blown up by tribesmen in December, when they came under attack.

Hadramawt has been shaken since December 20 by protests against the central government after the army killed tribal chief Said Ben Habrish and his bodyguards at a checkpoint.

Habrish's supporters 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.

The pipeline usually pumps about 120,000 barrels of oil per day, but production was halted after it was blown up on December 28.

The tribesmen struck another section of the pipeline again in early January after one of them was killed at an army checkpoint.

Attacks on oil and gas pipelines in Yemen are frequent. They are often carried out by heavily armed tribes as a lever to press for the release of jailed relatives, among other demands.