The UK has announced new sanctions against Moscow, while the British have been warned not to travel to Russia.

Foreign Minister Liz Truss said three more Russian banks would be sanctioned following the Ukraine invasion, including Russia’s largest, Sberbank.

He also announced that the UK would ban exports to Russia from the UK in a variety of “critical sectors”.

Acknowledging that the war “could last for months and years”, Ms Truss said the UK was “ready to make economic sacrifices” to support Ukraine and would maintain sanctions “for as long as necessary”.

The chancellor told the House of Commons that she was “determined to go much, much further”.

Shortly before his announcement, the Foreign Office advised Britons against traveling to Russia, citing “the lack of flight options available to return to the UK and the heightened volatility of the Russian economy.”

Before today, Britons were advised against all but essential travel to Russia after Vladimir Putin halted all flights to the UK last week in response to sanctions.

Live updates as the conflict enters day five

And Transport Secretary Grant Shapps said he had written to all UK ports asking them not to give access to any Russian-flagged, registered, owned, controlled, chartered or operated vessels.

Ms Truss said there will be a “complete freeze on the assets of all Russian banks in a few days” and legislation will be introduced to prevent the Russian state from incurring debt in the UK.

“With more than 50% of Russian trade denominated in dollars or pounds, our coordinated action with the United States will damage Russia’s ability to trade with the world,” he said.

Ms Truss said the ban on British exports to Russia will include high-end technological equipment, such as marine and navigational equipment, which will “reduce Russia’s military-industrial capabilities and cripple the Russian economy for years to come”.

She told MPs: “The next few days are likely to be even more difficult. The UK and our allies will face economic hardship as a result of our sanctions.

“But our difficulties are nothing compared to what the Ukrainian people are going through.

“The number of victims is increasing and more than 300,000 people have already been displaced. It is a fight for freedom and self-determination in Ukraine, but it is also a fight for freedom and democracy everywhere. And for the survival of a whole and free Europe. »

Earlier on Monday, the Kremlin claimed that Vladimir Putin had decided to put Russia’s nuclear deterrent forces on high alert on Sunday. by statements by Mrs. Truss.

According to the Interfax news agency, Kremlin spokesman Dmitry Peskov told a news conference: “Several representatives at different levels have made statements about possible altercations or even collisions and clashes between NATO and Russia.

“We believe that such statements are absolutely unacceptable.

“I would not call the authors of these statements by their names, although they are the British Foreign Secretary.” »

It is unclear what specific comments the Kremlin is referring to.

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Downing Street said the Kremlin’s attempt to blame Truss for escalating its nuclear alert was an attempt to “entertain” the situation on the ground in Ukraine.

Boris Johnson’s spokesman said the Kremlin’s latest comments were “very unnecessary” and added: “They should stop talking in those terms and defuse the situation.”