Heartbreaking vision has emerged from Syria's Idlib province, showing a father cradling the bodies of his nine-month-old twins.
Abdel Hameed al-Youssef describes how he and his young family tried desperately to escape as toxic gases were released during airstrikes in the area.
"I was right beside them. I took them outside with their mother. They were conscious, but 10 minutes later we could smell it and my children couldn't handle it any more. I left them to the medics and went to find my family."
Mr al-Youssef's wife and his children, Aya and Ahmed, were reportedly among 20 members of his family killed.
"I left Ahmed and Aya in good health. Why did this happen? I went to help other people and thought my children were OK. Now they're gone."
Rescue workers continue to find more terrified survivors hiding in shelters in the town of Khan Sheikhoun.
Dozens were killed during the attack that left residents gasping for breath and convulsing in the streets.
The World Health Organisation's Dr Peter Salama says if the attacks are confirmed as chemical, it marks "a level of barbarism not seen in recent times".
"We're working to help the doctors and nurses with the clinical management of these patients they're seeing, we're working to ensure they have adequate personal protective equipment to protect themselves as they treat the patients, and we're working to ensure they have the drugs and medical equipment to do so. The symptoms they're exhibiting are indeed consistent with the use of toxic chemicals. The symptoms might start with a runny nose or irritation of the eyes, it then quickly progresses to breathing difficulties, to muscular spasms and ultimately to convulsions and to coma, and of course to death."
The attacks have received worldwide condemnation and during an emergency debate at the UN Security Council there was little doubt over who was thought responsible.
Britain's ambassador to the UN, Matthew Rycroft, pointed the finger squarely at Syrian President Bashar al-Assad.
"This doesn't look like the work of terrorists. This doesn't look like the work of the opposition. This bears all the hallmarks of the Assad regime and the use of chemical weapons is a war crime."
One of Syria's chief allies was also caught in the cross hairs.
The United States ambassador to the UN, Nikki Haley, held up pictures of children killed in the attack, and criticised Russia for backing President Assad's government.
"If Russia has the influence in Syria that it claims to have we need to see them use it. We need to see them put an end to these horrific acts. How many more children have to die before Russia cares?"
But the Syrian government and Russia have been equally vehement in their denials.
In a statement broadcast on Syrian state television, government forces "categorically" denied using chemical weapons.
"The Syrian national army is incapable of carrying out these heinous criminal acts and hold the terrorist groups and those who stand behind them responsible for the use of chemical and poisonous substances, with no regard for the lives of innocent civilians, all with the aim of achieving their despicable goals and objectives."
Russia's Ambassador to the UN, Vladimir Safronkov, told the Security Council the poisonous gas came from a rebel chemical weapons depot hit by Syrian government air strikes.
"The Syrian air force conducted an air strike on the eastern end of Khan Sheikhoun on a large warehouse of ammunition and military equipment. On the territory of that warehouse, there was a facility to produce ammunition with the use of toxic weapons."
Rebel forces deny the claim.
Meanwhile, US President Donald Trump has strongly condemned the Syrian government in the wake of the attack.
Speaking at the White House during a visit by Jordan's King Abdullah, Mr Trump labelled the attack "a terrible affront to humanity"
"It crossed a lot of lines for me. When you kill innocent children, innocent babies, babies, little babies with a chemical gas that is so lethal - people were shocked to hear what gas it was - that crosses many, many lines beyond a red line - many, many lines."
Mr Trump repeated criticism of his predecessor, Barack Obama, for failing to act after threatening military action against the Syrian government in 2012.
But Mr Trump is yet to say what he will do to try and bring the now six-year conflict to an end.
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