The Syrian government said the air strike came from the US-led coalition targeting the Islamic State group

The United States is "certain" that it was a Russian air strike that killed three Syrian soldiers and wounded 13 others.

A senior US military official said it was not a coalition strike, but Syria's government has accused the US-led alliance of bombing the army camp and hitting troops loyal to President Bashar Assad.

The city of Der el-Zour, where the strikes are said to have been carried out on Sunday, is mainly held by the Islamic State group, but the Syrian government maintains a presence in some parts of it.

A US-led coalition has been striking at IS targets in Syria for the past year. France and the United Kingdom have recently joined in and have carried out air strikes of their own in Syria.

In a letter sent to the United Nations and published in Syrian state media, the government in Damascus said four aircraft belonging to the US-led coalition targeted the army camp in the eastern city.

In addition to the casualties, it said the attack destroyed armoured and other vehicles and a weapons and ammunition depot.

"This hampers efforts to combat terrorism and proves once again that this coalition lacks seriousness and credibility to effectively fight terrorism," the Syrian letter said.

Since the end of September, Russian planes have also pounded the Islamic State group and other insurgents in Syria fighting to topple Assad.

On Sunday, air strikes hit several IS positions in its de facto capital of Raqqa in northern Syria, killing and wounding at least 32 IS fighters according to several anti-IS activists. IS media accused the Russians of being behind those attacks and claimed civilians were killed.

PA Media