LONDON: Britain on Wednesday (Feb 21) imposed sanctions on six individuals in charge of the Arctic penal colony where Russian opposition leader Alexei Navalny died last week.

Western leaders have expressed outrage at the news from Russian authorities that Navalny, President Vladimir Putin’s most prominent domestic critic, had fallen unconscious and died in prison on Friday.

Those sanctioned, including the head and five deputy heads of the penal colony, will be banned from the UK and have their assets frozen, British Foreign Secretary David Cameron said in a statement.

“It’s clear that the Russian authorities saw Navalny as a threat and they tried repeatedly to silence him … no one should doubt the oppressive nature of the Russian system,” he said.

“Those responsible for Navalny’s brutal treatment should be under no illusion – we will hold them accountable.”

Cameron had vowed action on the matter on Saturday, while London summoned the Russian ambassador to make clear it held Russian authorities “fully responsible” for Navalny’s death.

Russia, which has denied involvement in the death of the 47-year-old former lawyer, said on Saturday that it was unacceptable for Britain to interfere in its internal affairs.