KIRKUK, Iraq - Islamic State militants launched a wave of pre-dawn attacks in and around the northern Iraqi city of Kirkuk on Friday, killing at least 14 people and setting off fierce clashes with Kurdish security forces that were still raging after sundown.
The assault appeared aimed at diverting attention from the Iraqi offensive to retake Mosul, and raised fears the extremists could lash out in unpredictable ways as they defend the largest city under their control and their last urban bastion in Iraq.
Multiple explosions rocked Kirkuk, and gunfire rang out around the provincial headquarters, where the fighting was concentrated. Smoke billowed over the city, and the streets were largely deserted out of fear of militant snipers. IS said its fighters targeted the provincial headquarters in a claim carried by its Aamaq news agency.
North of the city, three suicide bombers stormed a power plant in the town of Dibis, killing 13 workers, including four Iranian technicians, before blowing themselves up as police arrived, said Maj. Ahmed Kader Ali, the Dibis police chief.
Iran's Foreign Ministry spokesman, Bahram Ghasemi, condemned the assault, which he said also wounded three Iranian workers, according to the official IRNA news agency. It was not immediately clear if Iranians were targeted in other attacks.
The Turkmeneli TV station, which had earlier shown live footage of smoke rising from outside the provincial headquarters, said in a news bulletin that one of its reporters, Ahmet Haceroglu, was killed by a sniper while covering the fighting.
There was no immediate word on casualties among other civilians or the Kurdish forces in Kirkuk. Police and hospital officials could not be reached for comment.
Kirkuk is some 100 miles (170 kilometers) from the IS-held city of Mosul, where Iraqi forces launched a wide-scale offensive on Monday. IS has in the past resorted to suicide bombings in and around Baghdad in response to battlefield losses elsewhere in the country.
Kirkuk is an oil-rich city claimed by both Iraq's central government and the largely autonomous Kurdish region. Kurdish forces assumed full control of the city in the summer of 2014, as Iraq's army and police crumbled in the face of a lightning advance by IS.
Kemal Kerkuki, a senior commander of Kurdish peshmerga forces west of Kirkuk, said the town where his base is located outside the city also came under attack early Friday, but that his forces repelled the assault.
He said IS maintains sleeper cells of militants in Kirkuk and surrounding villages. "We arrested one recently and he confessed," he said, adding that Friday's attackers may have posed as displaced civilians in order to infiltrate the city. Kirkuk province is home to hundreds of thousands of people displaced by the conflict.
Iraqi and Kurdish forces backed by a U.S.-led coalition launched the multi-pronged assault this week to retake Mosul and surrounding areas — the largest operation undertaken by the Iraqi military since the 2003 U.S.-led invasion.
By Thursday, the Iraqi forces had advanced as far as Bartella, a historically Christian town some nine miles (15 kilometers) from Mosul's outskirts.
An Associated Press reporter traveling Friday with the Iraqi special forces saw homes along Bartella's main road painted with IS graffiti, including the first letter of a derogatory word in Arabic for Christians that the militants use to mark Christian property. Under IS rule, Christians must convert to Islam or pay a special tax.
IS graffiti was also sprayed on the inside walls of the town's church. Iraqi soldiers raised the national flag over the building and rang the church bell, signaling its liberation.
"Bartella was liberated yesterday, and today we are inside its church," Lt. Gen. Talib Shaghati declared. "I bring the good news to our Christian brothers that the church is liberated."
Elsewhere in Iraq, the country's top Shiite cleric called on forces taking part in the Mosul offensive to protect civilians, and for residents of Mosul, a mainly Sunni city, to cooperate with security forces.
"We stress today upon our beloved fighters, as we have before on many occasions, that they exercise the greatest degree of restraint in dealing with civilians stuck in the areas where there is fighting," the reclusive Grand Ayatollah Ali al-Sistani said in a Friday sermon read by an aide. "Protect them and prevent any harm to them by all possible means."
Some 3,900 people, or about 650 families, have fled Mosul and the nearby Hamdaniyah district since the operation began, according to Adrian Edwards of the U.N. refugee agency.
Ravina Shamdasani, of the U.N. human rights office, said it had "verified information" that IS forced 550 people to relocate to Mosul from the nearby villages of Samalia and Najafia on Monday, part of an "apparent policy of preventing civilians from escaping to areas controlled by Iraqi security forces."
Shamdasani reiterated concerns IS could use civilians as human shields, and said the office was investigating reports that the group had killed at least 40 civilians for suspected disloyalty. She did not provide further details.