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KIRKUK, Iraq, July 31 (Xinhua) -- Gunmen attacked two energy facilities in Iraq's northern province of Kirkuk on Sunday, killing at least four workers in one facility and detonated explosives in the other, a provincial security source said.

Huge fire rises from a fuel tank after gunmen stormed the oil field of Bai Hassan in northwest of the city of Kirkuk, Iraq, on July 31, 2016. Gunmen attacked two energy facilities in Iraq's northern province of Kirkuk on Sunday, killing at least four workers in one facility and detonated explosives in the other, a provincial security source said. (Xinhua/Ako Zhangna)

At least five gunmen wearing explosive vests stormed the oil field of Bai Hassan in northwest of the city of Kirkuk, some 250 km north of the Iraqi capital of Baghdad, the source said on condition of anonymity. The security forces shot dead one of them while the four others blew themselves up later after clashes with the troops, the source added.

The attackers managed to blow up two oil storage tanks inside, setting huge fire and sending column of black smoke above the area, the source said.

There is no immediate report about casualties among the oilfield workers and the security forces.

The security forces are in full control of the oil field after killing the last suicide bombers, and a search operation is underway inside the facility looking for any more attackers, the source added.

The attack in Bai Hassan is the second for the gunmen on Sunday morning, as militants broke into a gas facility in western the oil-rich province of Kirkuk and planted bombs in the facility after they shot dead four workers, the source said in earlier report.

The attackers fled the scene before the security forces retook control of the facility and defused the bombs, according to the source.

No group has so far claimed responsibility for the attack in the gas facility, but Islamic State (IS) militant group has previously targeted oil facilities in the province with explosives, repeatedly targeting oil wells at Khubbaz oilfield southwest of Kirkuk.

Iraq has been hit by a new wave of violence since the IS terrorist group took control of parts of Iraq's northern and western regions in June 2014.