Explosions lit up the skies with anti-aircraft fire over Damascus, the Syrian capital. File picture: Hassan Ammar/AP

Beirut - At least 40 troops allied with the Syrian government were killed overnight when airstrikes hit the country's eastern border with Iraq, a monitor said Monday.

The Britain-based Syrian Observatory for Human Rights said the airstrikes hit the town of al-Hari on the Syrian border with Iraq.

The watchdog could not immediately identify who carried out the strikes. 

Syrian state-run news agency SANA, citing a military source, accused the US-led coalition of carrying out the strikes against one of its positions in the town of al-Hari, south-east of al-Bou Kamal in eastern Syria.

A number of "martyrs were killed and others were wounded," SANA reported.

The observatory said the slain forces could be Iraqi or Lebanese nationals.

The pro-Iranian Lebanese Shiite movement Hezbollah has been fighting in Syria alongside Syrian President Bashar al-Assad's forces since the uprising started in 2011.