Italy's foreign minister Angelino Alfano on Tuesday deplored the suspected chemical attack in northwestern Syria in which at least 58 people were killed and dozens injured, calling it "a crime against humanity".
"The news of a chemical attack against defenceless civilians in Syria and the bombing of hospitals where victims were receiving treatment is distressing," Alfano said, referring to Tuesday's attack on the rebel-held town of Khan Sheikhoun.
"Italy will be at the forefront criticism of the attack at an emergency meeting of the United Nations Security Council requested by France and Britain," he went on.
"And tomorrow during the international conference on Syria taking place in Brussels, it will lead condemnation of the use of weapons of mass destruction against the Syrian people and demand that those responsible for this crime against humanity are identified."
UK-based watchdog The Syrian Observatory for Human Rights reported that strikes on Khan Sheikhoun by Syrian government or Russian warplanes had caused many people to choke.
Later, aircraft fired rockets at local clinics treating survivors, medics and activists said.
SOHR quoted medics as saying that they had been treating people with symptoms including fainting, vomiting and foaming at the mouth.
The pro-opposition Edlib Media Centre and the opposition Local Co-ordination Committees (LCC) network said the substance dropped was believed to be the nerve agent Sarin, which is highly toxic and considered 20 times as deadly as cyanide.
Syria's state-run news agency Sana quoted "the general command of the Syrian armed forces" as categorically denying that any chemical or toxic substance had been used on Tuesday in Khan Sheikhun.
"These have never been used in any circumstances or in any place they never will be in the future," it said.
The attack has drawn international condemnation