At least six army soldiers were killed when armed tribesmen launched an attack Wednesday on a military unit protecting an oil field in Yemen's southeastern province of Hadramout, an official told Xinhua.

The well-armed tribesmen clashed with army soldiers near Yemen's Masila oil field in Hadramout province, leaving at least six soldiers killed at the scene, the local government official said on condition of anonymity.

"The soldiers and tribesmen exchanged heavy gunfire in the oil firm protection unit near Ghayl Bawazir region in Hadramout. Up to 6 soldiers were killed," the government source said.

Meanwhile, a tribal chief told Xinhua on condition of anonymity that "about 20 French soldiers arrived in Hadramout to protect Total-run oil block 10."

Armed tribesmen have frequently attacked oil pipelines since 2011 to press the government to free their relatives from prison or provide their tribes with jobs.

Oil revenues support more than 70 percent of Yemen's state budget, while oil and gas products account for over 90 percent of the nation's exports.