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BAGHDAD, Oct. 21 (Xinhua) -- Dozens of Islamic State (IS) militants on Friday carried out multiple attacks in the Iraqi northern city of Kirkuk targeting security and local government buildings, as the Iraqi and Kurdish security forces are pushing to recapture territories around the city of Mosul in preparation for the final offensive on the IS last major stronghold in Iraq.

The attacks in Kirkuk began before dawn when dozens of IS militants, many wearing explosive vests, attacked the police compound, a building of Kurdish security, known as Asaysh, and some government buildings and mosques inside the city of Kirkuk, some 250 km north of the Iraqi capital of Baghdad, a local police source told Xinhua on condition of anonymity.

After fierce clashes with the security forces, the attackers and suicide bombers seized several buildings in southern and central parts of the city, including a police headquarters, Kurdish Asaysh, a mosque and houses, the source said.

The Kurdish security forces, backed by Kurdish reinforcement troops from the neighboring provinces of Sulaimaniyah and Arbil, surrounded the IS-held buildings inside the city, while clashes continued during the day, the source said.

By the end of the daylight, the troops managed to retake control of several buildings in the city neighborhoods, including Tis'in, Wasiti, Wahid Huzairan and al-Askari, but the clashes continued in the night in the neighborhoods of Domiz in southern Kirkuk and Raas al-Jeser in central part of the city.

Late in the afternoon, the security forces killed three IS militants who were fighting at a building in Wahid Huzairan neighborhood and freed some 20 civilians held hostages by the militants, the source said.

Several local Iraqi channels broadcast the fire exchange live for a few hours during the day, showing dozens of policemen, Peshmerga members and armed Kurdish civilians carrying their weapons and surrounding the occupied buildings.

The source could not give exact number of casualties by the clashes as the battles are underway, but said that at least 13 security members were killed and 37 others wounded, while more than 14 IS militants were killed, including six detonated their explosive vest.

In addition, an Iraqi journalist, who works for the local Turkmeneli channel, was killed by crossfire between IS militants and the security forces in central Kirkuk, the source added.

Authorities in the city imposed curfew and blocked the entrances of the city, as dozens of police and Kurdish security forces were deployed outside the government buildings and main streets, the source said.

Another attack targeted al-Debis power plant, some 35 km northeast of Kirkuk, when at least two suicide bombers entered the station sparking heavy clash with the guards, but the attacker took control of part of the facility and executed 16 workers, including four Iranians, the source said.

The Iranian victims were technicians of the Iranian Sunir company, which has been implementing a contract of expanding the power plant with the German Siemens company.

Later in the day, the security forces killed the suicide bombers and the situation in the plant is under control, the source added.

In Iraq's northern central province of Salahudin, two suicide bombers blew their explosive vests in the morning at the house of Sheikh Adnan al-Bazi, the leader of government-backed paramilitary Sunni tribal fighters, in the town of Mutasim, some 100 km north of the Iraqi capital Baghdad, a provincial security source told Xinhua.

The guards of the group's leader clashed with the attackers who managed to enter the house and detonated themselves, leaving three people killed and 15 others wounded, including Bazi himself and some of his family members, the source said.

The attack in Kirkuk came as the Iraqi security forces backed by anti-IS international coalition are carrying out a major offensive to drive out the IS militants from its last major stronghold in and around the city of Mosul in northern Iraq.

During the day, Iraqi security forces and allied Shiite paramilitary Hashd Shaabi units continued their advance in south of Mosul and recaptured three villages while moving north to the IS-held town of Shoura, some 30km south of Mosul, a security source from the Operations Command of Nineveh Liberation told Xinhua.

Meanwhile, heavy battles are underway in what is known as Nineveh Plain, which lies to the east and northeast of Mosul, the capital of Iraq's northern province of Nineveh.

On Oct. 17, Iraqi Prime Minister Haider al-Abadi, who is also the commander-in-chief of the Iraqi forces, announced the start of a major offensive to retake Mosul, the country's second largest city.

Mosul, some 400 km north of the Iraqi capital of Baghdad, has been under IS control since June 2014, when Iraqi government forces abandoned their weapons and fled.