Syrian president Bashar al Assad has questioned whether last week's alleged chemical weapons attack actually happened, saying there are "a lot of fake videos now".
Mr Assad was speaking in his first interview since the assault in the rebel-held town of Khan Sheikhoun on 4 April, in which more than 80 people were killed.
Asked by AFP TV who was responsible for the claimed attack, he said: "It's not clear whether it happened or not, because how can you verify a video?
"You have a lot of fake videos now, and you have the proof that those videos were fake, like the White Helmets, for example," he alleged.
"They are Al-Qaeda. They are Al-Nusra Front who shaved their beards, wore white hats, and appeared as humanitarian heroes, which is not the case."
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Expanding on his theme, Mr Assad questioned the images that appeared in the media.
"We don't know whether those dead children were killed in Khan Sheikhun," he said. "Were they dead at all?
"Who committed the attack, if there was an attack? What's the material? You have no information at all, nothing at all. No one investigated."
Denying any involvement whatsoever, the Syrian leader said: "A hundred percent for us, it's fabrication. We don't have an arsenal, we're not going to use it."
He also claimed the story was made up with the US attack on a Syrian airbase in mind.
"Our impression is that the West, mainly the United States, is hand-in-glove with the terrorists," he said.
"They fabricated the whole story in order to have a pretext for the attack."
He added he would only allow an investigation into the attack "when we make sure that unbiased countries will participate in this delegation in order to make sure that they won't use it for politicised purposes".
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On Wednesday, Russia vetoed a UN Security Council resolution demanding a probe, prompting Foreign Secretary Boris Johnson to say Moscow had put itself "on the wrong side of the argument".
Britain's ambassador to the UN also said UK analysis of samples from Idlib province had detected sarin or a sarin-like substance.
However, Vladimir Safronkov, Russia's deputy ambassador to the UN, said he was "amazed at this conclusion".
Prime Minister Theresa May says she believes it is "highly likely" Mr Assad's forces were behind the deaths, adding that "it is only the regime that has the capability to make such an attack".
Ties between Russia and the US have been strained in recent days, with Moscow attacking America's "primitive and loutish" rhetoric over Syria .
Following a meeting between US secretary of state Rex Tillerson and Russian counterpart Sergei Lavrov on Wednesday, Donald Trump warned relations were "at an all-time low".
The President later seemed to strike a more conciliatory note and said he expected "things will work out fine" between the US and Russia .
Meanwhile, Russian President Vladimir Putin said the "level of trust" had "not improved but has rather deteriorated" between the two countries.
The comment is telling because when Mr Trump came to power many thought US-Russia relations would improve from the low point reached during the Obama administration, which saw Russian diplomats expelled during the end of his presidency for alleged election hacking.