Turkey claims a Syrian airstrike killed three Turkish soldiers and wounded 10 others overnight, raising the ante in its military invasion of the Arab country.

A military statement on Thursday said the attack occurred at around 3:30 am (0030 GMT) in the course of a Turkish operation in northern Syria. 

It is the first time Turkey accuses Syrian government forces of killing its soldiers since Ankara launched its incursion, dubbed Euphrates Shield, into the Syrian territory on August 24.

In its invasion of Syria, the Turkish military is supporting militants, including the so-called Free Syrian Army (FSA), and militants who are fighting to topple the government of President Bashar al-Assad. 

Hundreds of Turkish troops are taking part in the operation, which President Recep Tayyip Erdogan said this week was pushing forward with the aim of capturing the Syrian city of al-Bab.

On Thursday, Syrian sources were quoted as saying that Turkey was building a military base in the Syrian town of Akhtarin in the northern Aleppo province.

Damascus has condemned Turkey's incursion into northern Syria, denouncing it as a "flagrant breach" of its sovereignty.