ERBIL, Iraq, July 23 (Xinhua) -- The Kurdish security forces Monday ended an attack by three gunmen who broke into the provincial government building in Iraq's northern city of Erbil, provincial official and a security source said.

Nawzad Hadi, the governor of Erbil, told reporters at a press conference that "three gunmen at 7:12 a.m. (0412GMT) broke into the provincial building, but the security forces managed to kill them all and regained control of the building after a counter attack that resulted in the killing of a civilian employee during the battle."

It was not immediately clear whether the civilian was killed by the gunmen or was caught in cross-fire with the security forces, Hadi said, adding that four security members were also wounded by the clashes.

Kurdish media reports identified the dead employee as Farhan Eliya Ibrahim, from the Christian minority who worked for years serving tea in the building.

"This is a terrorist act which will not undermine the will of the people of Kurdistan, and we reassure the citizens that the situation is under control," Hadi added.

For his part, Tariq Nouri, head of Asaiysh forces (Kurdish security forces), told the press conference that "the three gunmen have been identified as Erbil Kurdish residents, their names and addresses are now known to the Kurdish security forces."

Nouri declined to disclose further information about the attackers as an investigation into the incident is underway by the security forces.

Earlier in the day, Erbil's deputy governor Tahir Abdullah, said two gunmen wounded a policeman at the gate, broke into the building and fired with small arms on the security forces which rushed to the scene and surrounded the building.

Kurdish special forces later broke into the building, searching for the attackers room by room, he said.

Abdullah believed that the attackers are members of sleeper cells of the extremist Islamic State (IS) group as they shouted "Allahu Akbar" in Arabic, or God is Greatest, which is usually used by IS extremist militants.

Hours later, a local security source anonymously told Xinhua that "the Asaiysh 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 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.

During the past months, hundreds of IS militants fled their former urban strongholds in Mosul, Salahudin Province and Hawija area in the west of Kirkuk, after Iraqi forces took over these regions in major offensives.

On Dec. 9, 2017, Iraqi Prime Minister Haider al-Abadi officially declared full liberation of Iraq from IS after Iraqi forces recaptured all the areas once seized by the extremist group.

However, remnants of IS militants are still capable of carrying out attacks and suicide bombings against security forces and civilian targets from time to time.