LONDON: British Prime Minister Boris Johnson's office and the Treasury have called in finance bosses and regulators to discuss how to ensure recently-announced sanctions on Russia are effective, the BBC's political editor Laura Kuenssberg said on Twitter.

It is likely that Johnson will announce some additional military support for Ukraine, said Kuenssberg, adding that it was not clear what those will be.

UK unveils sanctions on Russian banks and oligarchs

Britain on Tuesday imposed sanctions on five Russian banks, Gennady Timchenko and two other billionaires with close links to Russian President Vladimir Putin.