At least three army soldiers were killed after armed tribesmen launched an attack on an oil field in Yemen's southeastern province of Hadramout on Saturday, a government official told Xinhua. "The tribal gunmen in vehicles attacked an on oil installation operated by Norwegian DNO in the suburbs of Hadramout province," the local official said on condition of anonymity. They killed three soldiers and kidnapped an engineer and two workers, the official said. An army officer near the scene confirmed to Xinhua about the incident, saying: "angered tribesmen attacked a military post guarding the oil field in Hadramout. Fierce armed confrontations followed the attack." Last week, attackers of a powerful tribe blew up a major oil pipeline in Yemen's Hadramout, halting the flow of oil. Yemen has seen frequent attacks by al-Qaida militants and armed tribesmen on oil pipelines as well as the country's main electricity grid. Yemen's oil production rapidly declined from 400,000 barrels per day at the beginning of the last decade to the current 270,000 barrels per day. The country's transitional government, which depends on oil exports for up to 70 percent of its budget, has bolstered security measures to protect the pipelines and prevent future attacks.