The Iraqi foreign ministry on Thursday sharply criticised a visit by Turkish Foreign Minister Ahmet Davutoglu to the disputed city of Kirkuk, saying it had not been informed of or approved the trip.

It is a new low for already-chilly relations between Iraq and its neighbour to the north, which have been marred by disputes, including oil exports by the autonomous Kurdish region to Turkey without Baghdad’s approval.

“It is not in the interest of Turkey or any other party to underestimate the national sovereignty and violate the rules of international relations and not comply with the most basic regulations in the relations of states and officials,” a statement on the foreign ministry’s website said.

“All of that was done without the knowledge or approval of the foreign ministry and without going to the official and diplomatic channels to organise this visit,” it said.

The foreign ministry statement termed the visit “blatant interference in Iraq’s internal affairs,” and said that Turkey should be ready for “the results of this action” and its potential “negative effects on relations between the two countries.”

The Kurdistan authorities also came in for criticism in the statement, which said: “We are surprised by the position of the government of the region, which facilitated the visit without the knowledge of the federal government and thereby violated its constitutional responsibilities.”

Davutoglu made his trip to Kirkuk while on a visit to Iraqi Kurdistan, whose leaders have long called for the incorporation of the ethnically divided oil city in their autonomous region in the north, against strong opposition from Baghdad.

Kirkuk province is part of a swathe of disputed territory in northern Iraq that along with oil contracts are the two main points of contention between Baghdad and the Kurdish regional government in Arbil.

Turkey and Iraq’s autonomous Kurdish region have said in a rare joint statement that they will tackle any threat from a violent group or organisation that exploits the power vacuum in Syria, an apparent reference to Kurdish rebels in Turkey and Syria.

Davutoglu met with the president of Iraq’s autonomous Kurdish region, Massoud Barzani, in northern Iraq to urge him not to support the Syrian political party “Our message has been well received,” Turkey’s state-run TRT television quoted Davutoglu as saying after the meeting late on Wednesday.

Turkey and the Iraqi Kurdish administration stressed their “deep concern regarding instability and chaos in Syria,” in a joint statement, the Foreign Ministry said early on Thursday.

“They also emphasised that any attempt to exploit the power vacuum by any violent group or organization will be considered as a common threat, which should be jointly addressed,” the statement said. “The new Syria should be free of any terrorist and extremist group or organisation.”

Turkey and Iraqi Kurds also agreed to co-ordinate their efforts with a view to helping Syrian people “to achieve their legitimate aspirations for a democratic, free and pluralistic Syria where all citizens will enjoy equal rights and freedoms.”

“In the new Syria, all ethnic, religious or sectarian identities should be respected and their rights should be guaranteed and protected,” the statement said.

Iraq’s Kurdistan region said it will resume oil exports during the first week of August as a confidence-building measure, after stopping them for more than four months following a row with Baghdad.