Russia has vetoed a UN Security Council resolution demanding a swift investigation into a chemical weapons attack in Syria.
Ten countries were in favour of the resolution drafted by Britain, France and the US. Russia and Bolivia were against, while China, Kazakhstan and Ethiopia abstained.
In addition to an investigation, the resolution would have condemned the use of chemical weapons in the rebel-held town of Khan Sheikhoun on 4 April.
The Syrian regime and its backers, including Russia, have denied President Bashar al Assad was responsible.
They have said the attack in Idlib province, which killed more than 80 people, was either a rebel provocation or the result of Syrian planes hitting a rebel weapons factory.
This is the eighth time that Russia has used its veto power at the UN Security Council to block action directed at Damascus since the bloody civil war began in 2011.
Foreign Secretary Boris Johnson said Russia's latest veto has put it "on the wrong side of the argument".
He added: "The international community sought to make clear that any use of chemical weapons by anyone anywhere is unacceptable and that those responsible will face consequences.
"So I am dismayed that Russia has once again blocked the UN Security Council and in so doing refused to condemn the use of chemical weapons or support a full UN investigation into the attack."
Nikki Haley, the US ambassador to the United Nations, has urged Moscow to stop protecting the Assad regime, and said it stands alone as "the rest of the world, including the Arab world, overwhelmingly comes together to condemn this murderous regime".
She told the council: "If the regime is innocent, as Russia claims, the information requested in this resolution would have vindicated them."
Earlier, Britain's ambassador to the United Nations, Matthew Rycroft, said that UK analysis of samples from the Syria chemical attack had detected sarin or a sarin-like substance.
But Russia's deputy ambassador to the UN, Vladimir Safronkov, said he was "amazed at this conclusion" - and challenged the claim.
"No one has yet visited the site. How do you know that?" he added.
Mr Safronkov also claimed America's cruise missile strikes on a Syrian airbase "was carried out in violation of international norms".
Russia - along with Britain, China, France and the US - are permanent members with veto powers, while the other 10 members are elected for two-year terms on a rotating basis.