Boris Johnson today declared Russia’s war “could now directly threaten the safety of all of Europe” after forces attacked a nuclear plant in Ukraine.
The Prime Minister demanded an emergency meeting of the UN Security Council in New York following an early-hours phone call with Ukraine’s President Volodymyr Zelensky.
UK Deputy Prime Minister Dominic Raab said the attack on the Zaporizhzhia nuclear plant was unlawful and it was difficult to believe it wasn’t deliberate.
He added: "The fact that the Russians kept on bombarding after there was the fire and the Ukrainian emergency rescue team were trying to get to that makes it doubly reprehensible."
A building at the power station - the largest in Europe - caught fire after it was attacked by Russia. While the reactor is under renovation, according to the power plant's spokesman, it still contains nuclear fuel.
According to the International Atomic Energy Agency (IAEA) the fire did not cause a change in the plant's radiation level. Nor had the shelling or fire caused any damage to "essential" equipment.
Ukraine today said Russian troops have now seized the plant. The IAEA will hold a press conference at 9.30am.
Boris Johnson spoke to Ukraine’s President about the “gravely concerning” situation before 2am.
According to No10, he said “the reckless actions of President Putin could now directly threaten the safety of all of Europe. He said the UK would do everything it could to ensure the situation did not deteriorate further.
“The Prime Minister said he would be seeking an emergency UN Security Council meeting in the coming hours, and that the UK would raise this issue immediately with Russia and close partners.
“Both leaders agreed a ceasefire was crucial.”
It comes ahead of crisis talks between Western ministers as Vladimir Putin steps up his assault on Ukraine's cities.
Liz Truss is joining fellow foreign ministers from Nato and the European Union for a series of meetings in Brussels as the allies show their support for Ukraine.
France last night said ranting Putin had warned the worst was yet to come in a phone call with French President Emmanuel Macron.
An Elysee Palace spokesman said: ‘President Putin expressed his very great determination to continue the offensive, the aim of which is to take control of the whole country.
"President Putin said the Russian Army operation was developing according to the plan’ and that it would ‘get worse if the Ukrainians do not accept surrender terms’."
Earlier in the night, the plant's spokesman Andriy Tuz told Ukrainian television that shells were falling directly on the Zaporizhzhia plant and had set fire to one of the facility's six reactors.
Several hours later, Ukrainian emergency services announced on social media that the fire had been extinguished.
Firefighters added that the blaze had been in the educational and training building of the plant and no one was harmed.
But Foreign Secretary Dominic Raab told BBC Breakfast: “It is very clear an attack like this, whether deliberate or just reckless, creates risk not just for the Ukrainians but for the region.”
Asked if it really could have been reckless rather than deliberate he replied: “I don’t know but it doesn’t really matter either way.
“If it was targeted, it’s even more reprehensible.
“But nonetheless when you’re engaged, and the laws on war are very clear on this, you must do your due diligence on your sites. I think it’s very difficult to believe it wasn’t done deliberately.
“But in any event it’s unlawful to attack a site like this, not to do your due diligence on it, and to keep bombarding it when there’s a fire and the emergency services are responding to it.”
It comes as the UK today launches its family visa scheme for fleeing Ukrainians who have relatives already settled in Britain.
Home Secretary Priti Patel is visiting Poland's border with Ukraine to highlight the visas on offer, with the government claiming up to 200,000 could be eligible.
But Labour demanded the government go further and help more people without family in the UK - after the EU said all Ukrainian refugees could come to live and work for three years.
Labour proposed an Emergency Protection Visa that would suspend all normal checks except biometrics and security, which could be carried out “swiftly” while refugees were on route.
Shadow Home Secretary Yvette Cooper said: “People need a simple and safe route to sanctuary right now. Most want to stay close to home, especially those who have had to leave relatives behind, but the UK must play its part to help people seeking support and safety in our country too.”