It still remains unclear what kind of substance was used

A child receives treatment at a hospital in the town of Maaret Al Noman.

International outrage is mounting over a suspected chemical attack that killed scores of civilians in a rebel-held town in northwest Syria on Tuesday morning.
AFP's correspondent in the town of Khan Sheikhoun saw lifeless bodies lying at a field hospital, which was itself hit in air strikes hours after the attack.
It remains unclear what kind of substance was used in the attack, but the World Health Organisation said on Wednesday that some victims appeared to show signs of exposure to "nerve agents".
If confirmed, it would be one of the worst chemical attacks since Syria's civil war began six years ago.
Air strikes hit the rebel-held town of Khan Sheikhun around 7am on Tuesday, and residents reported finding entire families "dead in their beds".
The Britain-based Syrian Observatory for Human Rights first reported that 58 civilians had died, but the monitoring group later updated the death toll to a total of 72, including 20 children and more than a dozen women.
Another 160 were wounded, with local medics telling AFP they had treated cases of suffocation, convulsions, pinpoint pupils, and rapid pulses.
Residents were rushed to clinics, and some victims were taken across the border for treatment in Turkey. Hours after the attack, as medics worked to treat the wounded in a hospital in Khan Sheikhun, two air strikes slammed into the facility and partially destroyed it.
The gruesome footage emerging from the town was met with widespread shock, including in Brussels where world powers have gathered to raise funds to deal with Syria's crisis.
Syria's opposition has accused the government of Bashar Al Assad of carrying out the strike, and warned that it "calls into question" efforts to bring an end to the bloody conflict. Rebel groups including Al Qaeda's former affiliate said they would take "revenge" against the regime and its backers, calling on allied fighters "to ignite the fronts".