Russian Federation and Syria claim the attack was fabricated.
There are fears that it could be a precursor to a campaign of cyber attacks by the Kremlin, and the Foreign Secretary said Britain must take "every possible precaution" to guard against it. "But it was the world saying that we've had enough of the use of chemical weapons", he added.
Boris Johnson has defended the decision to launch air strikes on Syria ahead of a Parliamentary debate on the issue, saying they were "right for the United Kingdom and right for the world".
"Finally the world has said enough is enough", he said.
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Mr Johnson said Mrs May will be making a statement in the House of Commons on Monday and it will give parliamentarians a chance to hold the executive to account.
The OPCW itself had declared that the Syrian regime's chemical weapons stockpile had been removed in 2014, only to confirm later that sarin was used in a 2017 attack in the northern town of Khan Sheikhun.
"If and when such a thing were to happen then clearly, with allies, we would study what the options were", he said. "The primary objective is to say no to the use of barbaric chemical weapons".
Labour is calling for a "War Powers Act" that would enshrine in law the need for the Government to seek Parliamentary approval before launching military action.
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On the same show, Jeremy Corbyn expressed his unease over the strikes and criticised the prime minister for not recalling Parliament to vote on the issue.
"This is not going to turn the tide of the conflict in Syria. And there is plenty of precedent for getting it done in this way", he said.
"Where is the legal basis for this?" he said.
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