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.”

The Turkish military also released a statement indicating that Russian officials had contacted them to express their “sadness and condolences” and added that “investigation and studies related to the event will be carried out by both sides.”

Two years ago, the Turkish military shot down a Russian jet near the Syrian border, but relations between the two nations have warmed slightly in the time since, despite the assassination of Russia’s ambassador to Ankara in December by a gunman who shouted, “Allahu akbar (God is greatest). Do not forget Aleppo! Do not forget Syria! Do not forget Aleppo! Do not forget Syria!”

Although Turkey and Russia each support opposing sides of the conflict in Syria, they have jointly targeted ISIS with air strikes.

Syria has been host to violent conflict for six years now.  The fighting has included Russia, Turkey, Iranian backed militias, the Islamic State and a U.S. led coalition working to combat Muslim extremists.  Russia has demonstrated themselves to be a key ally for Syrian president Bashar al-Assad, while Turkey has provided backing for rebel forces that oppose him.