Announcing the curbs, Foreign Secretary David Lammy said the UK wanted "to keep up the pressure" on Russian President Vladimir Putin, with a Russian defence minister, Pavel Fradkov, among those targeted by London.

Britain's top diplomat linked the sanctions to the work of Alexei Navalny, the Russian opposition leader who died in an Arctic prison colony last year in murky circumstances.

Lammy will meet his widow Yulia Navalnya while attending the Munich Security Conference of Western allies on Friday.

"Nearly a year on from the death of Alexei Navalny, I am honoured to meet with Yulia Navalnya and make clear our commitment to weaken Putin's attempts to stifle political opposition and crack down on the Kremlin's corrupt dealings globally," he said in a statement.

"We are calling on our friends and allies to continue to step up in the face of ongoing Russian aggression."

His comments come hot on the heels of US President Donald Trump and Russia's Vladimir Putin holding watershed talks this week about Moscow's three-year-old invasion, with the US leader announcing they had agreed to soon start Ukraine talks.

That has sparked unease in Kyiv and among its other allies, who fear a deal could be made over their heads.

The latest British sanctions, which impose UK asset freezes and travel bans, target three Russians who featured on the so-called "Navalny 50" list of figures accused of corruption, Lammy's foreign ministry noted.

Alongside Fradkov, London said it was targeting Vladimir Selin, head of an arm of the Russian Ministry of Defence, and Artem Chaika, whose extractives company supports Russian state-owned business.

The ministry added the curbs also hit two entities linked to Russia's nuclear energy giant Rosatom, "which are supporting Russia's military activity on the battlefield in Ukraine".