ISIL claims responsibility for deadly attacks targeting buildings and a power station in and around oil-rich city.
Military vehicles seen at a site targeted by ISIL fighters [Ako Rasheed/Reuters]
ISIL fighters have attacked multiple targets in and around the oil-rich city of Kirkuk, in a major assault that appeared aimed at diverting Iraqi and Kurdish forces from a massive push against Mosul, the armed group's last major stronghold in Iraq.
The coordinated attacks began early on Friday when fighters armed with assault rifles and explosives attacked a power station and government buildings, including the police headquarters.
ISIL, also known as the Islamic State of Iraq and the Levant, or ISIL, quickly claimed responsibility for the attacks in online statements.
In one of the incidents, at least three suicide bombers were killed as security forces foiled an attack on a former police complex in central Kirkuk.
Outside Kirkuk, at least 10 employees, including three Iranian nationals, where killed when gunmen stormed a power plant and then blew themselves up, according to authorities.
Al Jazeera's Hoda Abdel-Hamid, reporting from outside the city, said intense exchange of gunfire was still taking place in several districts of Kirkuk.
"It is a very volatile situation," Abdel-Hamid said. "The residents of Kirkuk have been told to remain indoors until further notice."
The sounds of gun shots and explosions that I am hearing now are unbelievable 😲 May God protect this city 🙏 #kirkuk #peshmarga
— Suren (@surennizam) October 21, 2016
According to our correspondent, "some of the ISIL fighters are holed up in one area in a school building, and in another area in a former police station".
"Witness told us that the ISIL fighters are still in control of certain areas in Kirkuk, neighbourhoods where Arabs and Turkmen live," Abdel-Hamid said.
A police colonel said at least six policemen and 12 ISIL fighters had been killed in the clashes, mostly in southern neighbourhoods, a toll confirmed by other officers, according to AFP news agency.
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 on Friday. He said the base is now under control.
According to Kerkuki, ISIL maintains sleeper cells in Kirkuk and the surrounding villages.
"We arrested one recently and he confessed," he told The Associated Press news agency, adding that the attackers may have posed as displaced civilians in order to infiltrate the city.
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Witnesses also reported gunfire and explosions, while live footage from the Kurdish Rudaw TV showed smoke rising from the city, where a curfew has been declared.
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The broadcaster quoted Kirkuk Governor Najmadin Karim as saying that fighters had not seized any government buildings.
The wave of attacks comes as the Iraqi government and Kurdish forces are making a major push to drive ISIL from Mosul, Iraq's second-largest city.
Iraqi officials said they had advanced as far as the town of Bartella, 15km from Mosul's outskirts, by Thursday.
ISIL, which still controls a swath of territory stretching across Syria and Iraq, has a history of launching diversionary attacks on distant fronts when it comes under pressure.
Kirkuk, an oil-rich city some 290km north of Baghdad and 170km southeast of Mosul, is claimed by both Iraq's central government and the country's Kurdish region.