A pro-opposition monitoring group says at least nine civilians have been killed in airstrikes by the US-led coalition purportedly fighting the Takfiri Daesh terrorist group in Syria.

The so-called Syrian Observatory for Human Rights said on Wednesday that the air raids hit the Albu Saraya alley in the Old City of Raqqah. The report said tens of civilians were also injured.

The coalition has been conducting airstrikes against what are said to be Daesh positions inside Syria since September 2014, without any authorization from the Damascus government or a UN mandate. The alliance led by Washington has repeatedly been accused of targeting and killing civilians. It has also been largely incapable of fulfilling its declared aim of destroying Daesh.

On Tuesday, at least 60 civilians lost their lives in similar strikes in Dayr al-Zawr province.

Syria's official SANA news agency reported on Wednesday that Damascus had asked the UN Security Council to hold accountable the United States and members of the international coalition for the death of civilians.

In two letters addressed to UN Secretary General Antonio Guterres and the president of the Security Council, the Syrian Ministry of Foreign Affairs and Expatriates complained that the coalition targeted civilians and the country’s infrastructure, referring to the Tuesday attacks. The ministry added that the coalition hits those who fight terrorism.

Separately, the observatory said the Daesh terrorists had chemical weapons in their possession in the areas that are still under their control in Raqqah.

The report added that terrorists planned to use the weapons when the battle over the city approached its end and the US-backed Syrian Democratic Forces (SDF) continued to advance in the city.

Daesh captured Raqqah in July 2014 and declared the city its stronghold in Syria.

The SDF forces have retaken more than half of Raqqah from Daesh over the past eight weeks, the observatory said.

Syria has been fighting different foreign-sponsored militant and terrorist groups since March 2011. UN Special Envoy for Syria Staffan de Mistura estimated last August that more than 400,000 people had been killed in the crisis until then.