THE Syrian air force has carried out a chlorine gas attack on a northern town, killing six people, according to activists, as Amnesty International said separate government air strikes on the Islamic State “capital” could amount to war crimes.

The Britain-based Syrian Observatory for Human Rights and the Local Co-ordination Committees said gas attacks on the town of Sarmin injured dozens more people.

An opposition official in the area said there were two attacks, the first targeting rebels while the second hit a residential area. He said the six killed were members of the same family, including three children.

A military official denied the claims and blamed the rebels fighting to topple President Bashar al-Assad.

Earlier, Amnesty said air strikes on the Islamic State stronghold of Raqqa on November 25 killed dozens of civilians.

The human rights group said it had documented a series of Syrian government air strikes between November 11 and November 29 that killed up to 115 civilians, including 14 children, in the city in northern Syria.

Raqqa has been the seat of Islamic State since it declared a caliphate in areas under its control in Iraq and Syria.

Amnesty said the “unlawful” killings violated international humanitarian law and some of the attacks could amount to war crimes.

The London-based group said the air strikes included attacks on a mosque and a busy market “crammed full of civilians” as well as some buildings not being used for military purposes.

Philip Luther, director of Amnesty’s Middle East and North Africa programme, said: “Syrian government forces have shown flagrant disregard for the rules of war in these ruthless air strikes. Some of these attacks give every indication of being war crimes.

“They have carried out repeated attacks on civilian areas without clearly identifying military targets, a blatant violation of the requirement to distinguish between civilians and military targets.”

Syrian authorities said at the time that the attacks were meant to target IS members and bases, but Amnesty said the evidence it gathered shows that, in most cases, no military targets could be identified.

On November 25, Syrian government forces bombed a number of civilian areas, striking a mosque, a busy market, shops, a transport hub, a storage facility and a residential building, Amnesty said.

Luther said: “The residents of Raqqa already have to endure the reality of life under brutal IS rule. Punishing an entire civilian population simply because the city where they live is now under IS control can never be justified.”

The main Western-backed opposition group, the Syrian National Coalition, said that in the Sarmin attack, helicopter gunships dropped four “barrel bombs”, of which two contained chlorine gas.

The coalition and the opposition official said about 70 people suffered breathing problems.

Amateur videos posted online and claimed to be from the attack show three children lying on hospital beds as medics try to assist them.

The footage shows an apparently dazed child slowly moving his head while lying on a hospital bed. The lifeless body of a woman lies on another bed.

“One of the infants, only a few months old,” a male voice says, shaking, as he films a baby on a gurney with liquid around its mouth. Two more infants with limp bodies are brought in, one by a man wearing a gas mask and another carrying a young girl.

“She’s still alive doctor,” a man checking the girl says. “Doctor, doctor, she is still breathing.”

The video, which could not be independently confirmed, appeared genuine and corresponded to other reports of the events depicted.

The attack came nearly two weeks after the UN Security Council approved a US-drafted resolution that condemns the use of toxic chemicals such as chlorine in Syria, while threatening militarily enforced action in case of further violations.

The resolution followed last month’s condemnation by the world’s chemical weapons watchdog of the use of chlorine in Syria as a breach of international law.

The Organisation for the Prohibition of Chemical Weapons’ fact-finding mission concluded “with a high degree of confidence” that chlorine was used on three villages in Syria last year, killing 13 people.