US President Joe Biden has met the wife and daughter of Alexei Navalny, the Russian opposition leader who died last week in a prison camp, and called him “a man of incredible courage”.

Biden, speaking to reporters in California on Thursday, reiterated that Washington plans to impose a wide array of sanctions on Russia and its leader Vladimir Putin following Navalny’s death.

Navalny, 47, fell unconscious and died suddenly on Friday after a walk at the Polar Wolf penal colony above the Arctic Circle where he was serving a three-decade sentence, the prison service said.

“He was a man of incredible courage and it’s amazing how his wife and daughter are emulating that,” Biden said after meeting Navalny’s wife Yulia and daughter Dasha.

“I know that we’re going to be announcing the sanctions against Putin, who is responsible for his death, tomorrow.”

Under Secretary of State Victoria Nuland on Thursday said some of the “hundreds and hundreds and hundreds” of sanctions to be unveiled in the coming days would target those responsible for Navalny’s death, but most would hit “Putin’s war machine” and close gaps in existing sanctions regimes.

The new measures are timed to mark the second anniversary of Russia’s full-scale invasion of Ukraine.

In a statement released before Biden spoke to reporters, the White House said the president conveyed his “heartfelt condolences” to Navalny’s family.

During the meeting in California, he expressed his admiration for Navalny’s “extraordinary courage and his legacy of fighting against corruption and for a free and democratic Russia in which the rule of law applies equally to everyone”, the White House said.

– AAP