Britain said on Friday it had imposed its latest round of sanctions against Russia over its invasion of Ukraine, targeting Russian President Vladimir Putin's financial network, including his ex-wife and cousins.

"We are exposing and targeting the shady network propping up Putin's luxury lifestyle and tightening the vice on his inner circle," foreign minister Liz Truss said in a statement.

"We will keep going with sanctions on all those aiding and abetting Putin's aggression until Ukraine prevails."