The Iraqi government has called on the Turkish government to withdraw its more than 100 training troops from northern Iraq, saying the activity is a breach of its sovereignty.

In a statement released on Saturday, the Iraqi foreign ministry said the Turkish troops entered "without the request or authorisation from the Iraqi federal authorities," which is a "serious breach of Iraqi sovereignty."

The foreign ministry described Turkey's move "an incursion," reports said.

The statement also called on Turkey "to respect good neighbourly relations."

On Friday, 130 Turkish soldiers equipped with heavy weapons were deployed at a military base on the outskirts of the city of Mosul, which is currently held by the Islamic State (ISIS), according to the Daily Sabah newspaper.

"Around one regiment armoured with tanks and artillery has entered the northern Nineveh area,'' the Iraqi Prime Minister's media office reported.

A source told Reuters that the U.S.-led anti-ISIS coalition was aware of Turkey's move. "Turkish soldiers have reached the Mosul Bashiqa region. They are there as part of routine training exercises. One battalion has crossed into the region. They are training Iraqi troops.''

But two U.S. defence officials clarified that Turkey's deployment is not part of the efforts of the U.S.-led coalition battling the ISIS.

Mosul, Iraq's second biggest city, was seized by ISIS in June 2014 and has been fully governed by militants ever since. Moreover, the extremist group captured large stockpiles of weapons and ammunition that were stored in the city.

The Turkish intrusion into Iraq came shortly after questions were raised by countries like Russia, Iran as well as Iraq over Turkey's true motives in the campaign against ISIS.

Russia earlier divulged Turkey's alleged illegal oil trade with ISIS after tensions heightened between the two countries following the downing of the Russian Su-24 bomber by a Turkish F-16 jet last month.

Turkey claims the Russian warplane violated its airspace but Moscow and even some U.S. officials say the Russian plane was over Syrian air space when it was shot down.

To prove its claims, Russia has presented photos and videos showing ISIS oil trucks effortlessly crossing the Syrian border into Turkey in militant-controlled areas, reports said.

The accusations were quickly dismissed by Turkish President Recep Tayyip Erdogan.