Turkey's prime minister will this week pay a critical visit to Iraq, President Recep Tayyip Erdogan said on Wednesday, after tensions soared to unprecedented levels ahead of the operation to recapture Mosul.

Ankara has been concerned over the role of Shiite pro-Tehran militia in the operation to take the majority Sunni second city of Iraq from Islamic State (IS) jihadists.

"We are watching all actions aimed at starting a confessional conflict in Iraq," Erdogan said in a speech in Ankara.

He said that Prime Minister Binali Yildirim and a delegation would be making a visit to Iraq starting on Friday.

"We want to bring our relations to a better level after they ground to a halt in recent times."

Ankara has been largely left on the sidelines in the Mosul operation and the tensions led to a bitter public spat between Erdogan and Iraqi Premier Haider al-Abadi.

Erdogan last year told the Iraqi leader to "know your place" and even said "you are not at my level".

Not to be outdone, Abadi hit back by mocking Erdogan's appearance on FaceTime to rouse supporters on the night of the failed July 15 coup.

But on December 30, Erdogan spoke to Abadi by telephone for the first time since the row, Turkish media said.

Meanwhile, Deputy Prime Minister Numan Kurtulmus said earlier this week that a "new era" was starting in Turkey's relationship with Iraq's leaders.

Ruled for nearly half a millennium by the Ottoman Empire, Mosul is considered by mainly Sunni Muslim Turkey to be part of its natural sphere of influence in the Middle East.

Ankara has insisted Mosul must keep its Sunni Arab Muslim majority which it had before IS took over the city from woefully unprepared Iraqi troops in 2014.

Before the emergence of IS in Iraq, Turkey had major ambitions for Mosul, opening a vast consulate but then finding its entire 49 strong staff was taken hostage by the jihadists in June 2014.

The hostages were later freed in September 2015 amid murky circumstances and, symbolically, the consulate building was destroyed in a US-led coalition air strike in April 2016.