Syria's government has accused the US-led coalition of launching air strikes on a Syrian army camp that killed three soldiers and wounded 13.

The government has sent a protest letter to the UN over the incident, which took place in the country's east.

If confirmed, the air strikes would mark the first time coalition forces fighting the Islamic State group in Syria and Iraq have attacked Syrian government forces.

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 of Deir el-Zour on Sunday night.

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

The city, in the province also called Deir el-Zour, is mainly in the hands of the Islamic State but the Syrian government still holds some parts of the city.

"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.

The Syrian Observatory for Human Rights, which tracks the Syrian conflict through a network of activists on the ground, also reported the incident.

According to the Observatory, in Syria's overcrowded skies, the aircraft behind the incident in Deir el-Zour are "believed" to belong to the anti-IS coalition.

The planes hit the camp known as "Sa'iqa" the Observatory said, though it gave a slightly different account for its location, saying the camp is near the village of Ayyash in the western countryside of Deir el-Zour.

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.

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