SAN’A, Yemen (AP)- Tribesmen attacked an oil installation in Yemen and then clashed with government troops Thursday, leaving 12 people dead, a local official said. It was the second attack on the country’s oil industry this week.

The clash in Shabwa province, about 136 miles southeast of the Yemeni capital San’a, broke out after men from the Bani Harith clan attacked a Ukrainian-run oil installation, said the province’s governor, Mohammad Ali Ruwashan.

Six government troops and six tribesmen were killed in the clash. One of the dead was Capt. Abdullah Allwan, the Yemeni commander of the installation’s guard unit. Ruwashan said six people were wounded in the shootout.

On Monday, unidentified saboteurs bombed an oil pipeline in nearby Marib province, a government official said. The attack halted the flow of oil and added to concerns in the world oil markets about adequate supplies for heating fuel in the approaching winter. Oil prices hit record highs this week.

There was no immediate comment from the government on the latest clash but Yemen’s defense minister was said to have been dispatched to the area.

Tribal clashes are common in Yemen, an impoverished nation where tribesmen often reach for their guns to settle arguments. Tribesmen accuse the government of backing down on pledges to employ a large number of them in the oil installations.

Al-Qaeda militants have been active in sabotage operations targeting oil pipelines and power stations in the country.

In June, Yemeni security arrested two men suspected of al-Qaeda links who confessed to an unsuccessful attempt to blow up an oil pipeline with TNT near the port city of Aden.

In June, five government troops were killed and five were wounded in a clash with tribesmen demanding jobs in oil fields in Marib.

Yemen produces 330,000 barrels of oil a day. In August, al-Qaeda militants attacked a power station and a government building in Marib, some 85 miles east of the capital, San`a, causing a major power outage.