Boris Johnson said Russian President Vladimir Putin has “chosen a path of bloodshed and destruction” with his attack on Ukraine and that the UK and its allies would respond “decisively”.

It came as Ukraine’s president declared martial law, while Russia’s military said it had targeted Ukrainian air bases and other military assets and had not targeted populated areas.

A Downing Street spokesperson said the Prime Minister will chair a Cobra committee meeting at 7.30am to discuss the response to the “horrific attacks”.

In a statement on Twitter, Mr Johnson said he had spoken with Ukrainian President Volodymyr Zelensky to discuss “next steps”.

“I am appalled by the horrific events in Ukraine and I have spoken to President Zelenskyy to discuss next steps,” he said.

“President Putin has chosen a path of bloodshed and destruction by launching this unprovoked attack on Ukraine.

“The UK and our allies will respond decisively.”

Russia declares war on Ukraine

Mr Putin announced the action during a televised address early on Thursday morning, saying the move was a response to threats from Ukraine.

He said Russia does not have a goal to occupy Ukraine, but the responsibility for bloodshed lies with the Ukrainian “regime”.

He also warned other countries that any attempt to interfere with the Russian action would lead to “consequences they have never seen”.

Mr Putin accused the US and its allies of ignoring Russia’s demand to prevent Ukraine from joining Nato and offer Moscow security guarantees.

He said the Russian military operation aims to ensure a “demilitarisation” of Ukraine, adding that all Ukrainian servicemen who lay down arms will be able to safely leave the zone of combat.

Explosions in Ukraine

Explosions could be heard in the Ukrainian capital of Kyiv shortly after Mr Putin’s address, while explosions were also reported in the cities of Odesa and Kharkiv.

Ukraine’s border guard agency said the Russian military attacked the country from neighbouring Belarus.

The agency said that the Russian troops unleashed an artillery barrage as part of an attack backed by Belarus. They said the Ukrainian border guards were firing back, adding that there was no immediate report of casualties.

Videos on social media show bomb sirens sounding in Ukraine’s capital city of Kyiv.

Explosions can be heard on CNN during a report from Kyiv minutes after Putin declared war on Ukraine.

Foreign Office minister James Cleverly promised the UK will respond.

He tweeted: “Putin’s attack on Ukraine is unprovoked and unjustified.

“We condemn this action in the strongest terms.

“The UK will work with our international partners to respond to this act of (aggression).”