China says ‘no comments’ on Alexei Navalny death: 'Russia's internal affair'

Alexei Navalny, the Kremlin's most prominent critic, died on Friday in an Arctic prison, Russian officials said.

China's foreign ministry declined to comment on Saturday on the death of Russian opposition leader Alexei Navalny, describing it as "Russia's internal affair".

Flowers and tributes are left opposite the Russian embassy, to commemorate the death of Alexei Navaln. (AP)

"This is Russia's internal affair. I will not comment," the Chinese Foreign Ministry's Spokesperson's Office said in response to a question from AFP.

Navalny, the Kremlin's most prominent critic, died on Friday in an Arctic prison, Russian officials said, a month before an election poised to extend President Vladimir Putin's hold on power.

His death after three years in detention and a poisoning that he blamed on the Kremlin, deprives Russia's opposition of its figurehead at a time of intense repression and Moscow's campaign in Ukraine.

Beijing and Moscow are staunch allies and have strengthened their relationship even as Western countries have turned their backs on Russia over its military invasion of neighbouring Ukraine.

Both sides have also made much of the personal relationship between the two leaders, and China's president Xi Jinping has referred to his Russian counterpart Putin as his "good friend".