The Kremlin has confirmed that Russian war planes have killed three Turkish soldiers in an wayward air strike in al-Bab in northern Syria.
Russian President, Vladimir Putin, has expressed his condolences to his Turkish counterpart in a telephone conversation.
Eleven others were wounded in the attack.
Earlier five Turkish soldiers died in clashes with ISIL fighters
The casualties are in addition to the five killed on Wednesday.
It comes as the bloody battle for the ISIL held al-Bab intensifies.
Reports suggest that al-Bab is surrounded on all sides and ISIL fighters have been driven into city centre.
The push for al-Bab comes as Turkey attempts to convince the Trump administration that Ankara is a reliable ally after President Obama supported Kurdish groups in the fight against ISIL.
New CIA head Mike Pompeo is currently on a visit to Turkey.