Days after Iraqi forces began an offensive to recapture the "Islamic State of Iraq and the Levant" (ISIL) group’s stronghold of Mosul , 25 villages and towns on the outskirts of the Ninawa province city have already been liberated, officials tell Diyaruna.

Since Monday (October 17th), Iraqi forces, supported by the international coalition, have liberated more than 300 square kilometres around Mosul, Ninawa operations commander Nejim Edin Karim al-Jubury said Friday (October 21st).

"Twenty five villages and towns have been captured, the last of which were the villages of Bartala, al-Homdiya and Jabal al-Asfar," he told Diyaruna.

More than 300 ISIL militants were killed in the battles, he said.

Use of human shields

ISIL fighters may be preparing to use civilians as human shields , or simply kill them, rather than let them be liberated, the UN said Friday.

UN human rights chief Zeid Raad al-Hussein said his office had reports that civilians were being held close to ISIL fighter positions in Mosul, possibly as a buffer against advancing Iraqi forces, AFP reported.

"There is a grave danger that ISIL fighters will not only use such vulnerable people as human shields but may opt to kill them rather than see them liberated," al-Hussein said in a statement.

Separately, al-Hussein said his office had reports that the militants forced an estimated 200 families to walk from the nearby Samalia village to Mosul last week.

Another 350 families were forced to Mosul from Najafia, according to the rights office.

Those forced displacements were consistent with ISIL's "apparent policy of preventing civilians from escaping to areas controlled by the Iraqi security forces", he added.

ISIL attacks Kirkuk in Mosul diversion

Also on Friday, ISIL fighters, some of them wearing suicide vests, attacked the nearby city of Kirkuk, in an apparent effort to divert the thousands of troops and militiamen closing in on Mosul, AFP reported.

The assault, together with another further north, left at least 22 people dead.

Kirkuk, currently under Kurdish control, woke up to find ISIL fighters spreading across several neighbourhoods.

An AFP correspondent saw a group of men carrying rifles and grenades and wearing "Afghan-style clothes" walk down one street in the city.

At least five suicide bombers struck government targets in the city, including the main police headquarters, in a co-ordinated attack claimed by ISIL, that began in the middle of the night.

Gunfire and explosions echoed across the city all morning, residents said, and live footage on local television showed street battles in several neighbourhoods.

"Our security forces are working relentlessly to eliminate all these terrorist cells by the close of day," Col. Arkan Hamed, from the provincial police, said.

Also on Friday morning, gunmen wearing suicide vests stormed a power plant being built by an Iranian company near Dibis, a town south-east of the Mosul offensive's main area of operations, and just 40 kilometres from Kirkuk.

"Three suicide bombers attacked the power plant at around 6 a.m., killing 12 Iraqi administrators and engineers and four Iranian technicians," Dibis mayor Abdullah Nureddin al-Salehi said.

A police lieutenant colonel confirmed the casualty toll from the attack, which was also claimed by ISIL.