The Prime Minister has confirmed that British nationals are among those caught up in the aftermath of a huge blast in the Lebanese capital Beirut.
Boris Johnson said the Government is "ready to provide support in any way we can", and Foreign Secretary Dominic Raab said the UK stands in solidarity with Lebanon.
In a tweet, Mr Johnson said: "The pictures and videos from Beirut tonight are shocking. All of my thoughts and prayers are with those caught up in this terrible incident.
"The UK is ready to provide support in any way we can, including to those British nationals affected."
All staff at the British embassy in Beirut are accounted for, but some have sustained "non-life-threatening injuries".
A spokesman for the Foreign Office said: "All Embassy staff are accounted for. A small number have sustained non-life-threatening injuries and where necessary are receiving medical attention."
Videos of a huge mushroom cloud rising above the Middle Eastern city were shared extensively on social media on Tuesday evening local time.
At least 70 people were killed and 3,000 injured, with bodies buried in the rubble, officials said.
While the cause of the blast was not immediately clear, speculation suggested an accidental explosion linked to the storage of dangerous chemicals, although US president Donald Trump said American military officials felt it may have been a bomb attack.
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Abbas Ibrahim, chief of Lebanese General Security, said the blast might have been caused by highly explosive material that was confiscated from a ship some time ago and stored at the port.
Local television channel LBC said the material was sodium nitrate.
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Witnesses reported seeing a strange orange-coloured cloud over the site after the explosion. Orange clouds of toxic nitrogen dioxide gas often accompany an explosion involving nitrates.
In a tweet, Mr Raab said: "My thoughts and prayers are with those affected by the devastating explosion in Beirut today.
"The UK stands in solidarity with the people of Lebanon and is ready to offer help and support, including to those British nationals impacted."