UK's Johnson warns Putin: invading Ukraine would be a costly mistake

British Prime Minister Boris Johnson records an address to the nation, to provide an update on the booster vaccine COVID-19 programme at Downing Street, London, Britain December 12, 2021. Kirsty O'Connor/Pool via REUTERS

LONDON (Reuters) - British Prime Minister Boris Johnson warned Russian President Vladimir Putin in a call on Monday that any destabilising action against Ukraine would be a strategic mistake with significant consequences, Downing Street said.

"The Prime Minister emphasised the UK's commitment to Ukraine's territorial integrity and sovereignty, and warned that any destabilising action would be a strategic mistake that would have significant consequences," a spokesman said.