A Russian jet accidentally killed three Turkish soldiers in northern Syria due to a mistake in coordination between Turkish and Russian militaries, Turkey’s Deputy Prime Minister Numan Kurtulmus said on Friday.

“According to the initial findings, the incident is a result of incorrect coordination, an incident that happened unwillingly,” Xinhua news agency quoted Kurtulmus as saying.

He added that the coordination mistake will be revealed over an investigation, local broadcaster CNNTurk reported.

Kurtulmus underlined the need for closer coordination with Russia to avoid such incidents.

On Thursday, a Russian war-jet, conducting airstrikes against Islamic State (IS) targets in al-Bab town of Syria, hit a building where Turkish Armed Forces units were placed, killing three soldiers and wounding 11 others, according to the Turkish Armed Forces.

Kremlin Spokesman Dmitry Peskov said on Thursday that the airstrikes were launched based on coordinates provided by the Turkish military.

“It was a lack of coordination in providing coordinates. That is how I would formulate it,” Peskov said.

On Thursday, Russian President Vladimir Putin talked to the Turkish President over telephone and expressed sorrow.