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Security personnel gather outside Erbil provincial government building at Erbil, Iraq, July 23, 2018. The Kurdish security forces on Monday killed three gunmen who broke into the provincial government building in Iraq's northern city of Erbil, a local security source said.(Xinhua/Yasser Jawad)

ERBIL, Iraq, July 23 (Xinhua) -- The Kurdish security forces on Monday killed three gunmen who broke into the provincial government building in Iraq's northern city of Erbil, a local security source said.

"The Asaiysh forces (Kurdish security forces) regained control on the provincial government building in Erbil after killing two terrorists on the second and another one on the third floor," the source told Xinhua on condition of anonymity.

"The troops also managed to release three people who apparently were taken hostages by the attackers, while they continued searching the building to secure the place," the source said.

As the largest city in northern Iraq, Erbil is both the capital of its namesake province and the semi-autonomous region of Kurdistan.

No group claimed responsibility for the attack in Erbil, some 350 km north of Iraq's capital Baghdad, which has been relatively calm since the U.S.-led invasion in 2003.

However, the security source said the Islamic State militant group could be behind the attack, as the security forces hold the fingerprints of its members.