BAGHDAD: Iraq made a formal protest to Turkey’s envoy in Baghdad Friday after the Turkish foreign minister made a surprise visit to an oil-rich Iraqi city claimed by both the central government and the country’s autonomous Kurdistan region.

In response, Turkey summoned the Iraqi ambassador in Ankara and warned Baghdad to be “careful” in its remarks.

The latest in a series of diplomatic spats and tit-for-tat summoning of envoys between the neighboring countries is likely to worsen already strained relations.

Turkish Foreign Minister Ahmet Davutoglu traveled to Kirkuk Thursday after visiting the regional president in Irbil, the capital of Iraqi Kurdistan.

But Iraq’s Foreign Ministry accused Turkey of violating its constitution with the visit, saying that Davutoglu had neither asked for nor obtained permission to enter Kirkuk.

A junior minister at Iraq’s Foreign Ministry handed Turkey’s charge d’affaires a protest letter Friday, a strongly worded statement from the Foreign Ministry said.

“The note also included a demand by the Iraqi government [for an] urgent explanation from the Turkish government,” it added.

Later in the day, the Turkish Foreign Ministry called in Iraq’s top diplomat in Turkey, an official said.

“The Turkish foreign minister made the visit [to Kirkuk] in a transparent way. There is no secret agenda,” the official from the Foreign Ministry said on condition of anonymity.

He added that Davutoglu had consulted with Kurdish officials in Irbil before going to Kirkuk in what was called the first visit to the city by a Turkish foreign minister in 75 years.

Relations between Iraq, close to Shiite Iran, and Sunni Muslim regional power Turkey, were tested after the United States’ troops pulled out of Iraq last year and the government immediately tried to arrest one of its Sunni vice presidents.

He fled first to Kurdistan and later to Ankara, where he was given refuge.

Iraqi Prime Minister Nouri al-Maliki and Turkish premier Recep Tayyip Erdogan traded insults at the time.

Baghdad’s Arab-led central government and ethnic Kurdish officials are locked in a protracted dispute over who controls territory and oilfields along their internal border.

Kirkuk, which possesses huge crude oil reserves, is one of those disputed areas.

Iraq and Turkey are also at odds over the conflict in Syria.