Three Turkish soldiers were killed and eleven others were injured when a Russian air strike accidentally hit a building occupied by the Turkish military in Syria on Thursday.

“During an operation by a Russia Federation warplane against Islamic State targets in the region of the Euphrates Shield operation in Syria, a bomb accidentally hit a building used by Turkish Army units,” the Russian military said in statement.

The Kremlin promptly issued a statement regarding the accident that indicated that Russian president Vladimir Putin had already been in contact with his Turkish counterpart in order to express his “condolences over a tragic incident which resulted in the deaths of several Turkish troops in the al-Bab area.”

According to the Russian statement, it was a lack of coordination between Moscow and Ankara that led to the tragic accident and the two world leaders agreed to “increase military co-operation during operations in Syria against IS militants and other extremist organizations.”