BEIRUT: An activist group said Tuesday government forces had carried out a poison gas attack that killed six people in the northwest, and medics posted videos of children suffering what they said was suffocation.
A Syrian military source described the report of an attack in the village of Sarmin in Idlib province as propaganda. "We confirm that we would not use this type of weapon, and we don't need to use it," the source said.
The Syrian government has previously denied accusations that it has used chemical weapons in the four-year-old war.
An army statement said many militants were killed in other areas of Idlib province overnight in clashes.
The Syrian Observatory for Human Rights, which is based in Britain and tracks the conflict through a network of sources, said the six dead included a man, his wife and their three children. It cited medical sources as saying they died as a result of gas released from barrel bombs dropped on Monday evening and that the chemical used was likely chlorine.
Dozens more people were wounded in the attack, the Observatory said. Reuters could not independently verify the report.
The Idlib branch of the Syrian Civil Defense rescue organisation posted seven videos on YouTube, some at nighttime and some in a medical center.
One video showed three children and a woman, all apparently unconscious, in a medical center. A voice off camera said the name of the village, Sarmin, and Monday's date.
"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 Syrian Civil Defense, also know as the "White Helmets" for the hard hats they wear, includes more than 2,000 humanitarian volunteers who work as first responders in a country where the medical infrastructure has broken down
Another video posted by the group and shot at night showed a very young girl, naked except for underwear and pink shoes, being doused in liquid by people wearing white helmets, her horrified expression illuminated by their headlamps shining on her face.
The Syrian Civil Defense said on Twitter there had been more than 100 casualties, including its own volunteers.
The reports came a day after Kurds in neighboring Iraq said that Islamic State insurgents used chlorine gas against military police and peshmerga forces in December and January. An officer said the gas was used three times, and that a number of military police were treated in hospital.
A U.N. inquiry found in late 2013 that sarin gas had likely been used in several rebel-held districts of the Syrian capital Damascus in August 2013, where hundreds of people were killed.
The inquiry was only looking at whether chemical weapons were used, not who used them. The government and the opposition have each accused the other of using chemical weapons during the civil war which has killed 200,000. Both sides deny it.
Assad agreed with the United States and Russia to dispose of his chemical weapons after hundreds of people were killed by sarin gas on the outskirts of the capital.
The Organization for the Prohibition of Chemical Weapons also said it had "compelling evidence" that chlorine gas was used in rebel-held villages in northern Syria last year. It did not say who carried out the attack.
Officials in Washington regularly accuse Assad of gassing his own people and say he has lost all legitimacy. But U.S. Secretary of State John Kerry said Sunday that Assad should be included in negotiations to reach a political transition, although a spokeswoman later explained that Kerry was not specifically referring to Assad.
The Syrian Foreign Ministry said Tuesday that France and Britain were "still engaging in policies that embroil the European Union in the ongoing aggression against Syria."
The statement, released after a cabinet meeting, appears to be an attempt to drive a wedge between Assad's greatest enemies in Europe, Britain and France, and other European Union states. The Syrian government has said it is willing to reengage with countries who stop supporting insurgents.
Opposition activists have reported many chlorine attacks over the past year, which they said occurred when explosive canisters were dropped from army helicopters.
Khaled Khoja, president of the opposition National Coalition, blamed Assad Tuesday for the most recent reported attack: "The psychopathic dictator continues to kill by chemicals and challenges the international laws."
Hamish de Bretton-Gordon, an expert on biological and chemical weapons, said there had been several chlorine bomb attacks in recent days in the area.
"On the face of it, the video of the attack looks genuine. While chlorine itself it not that deadly, it is being very effectively used as a weapon of terror, first in Syria and now in Iraq. It killed three children, who are too little to run away after an attack."