Slovenia's top officials have expressed shock and sadness at the death of jailed Russian opposition leader Alexey Navalny, describing it as a major blow to democracy, freedom and human rights.

"This is a heart attack on democracy in Russia," President Nataša Pirc Musar wrote on X, expressing her condolences to Navalny's family.

"Today is a sad day for human rights all around the world," Prime Minister Robert Golob wrote on the same social network. "We have lost one of the most prominent human right defenders and fighters for freedom and justice," he added.

Foreign Minister Tanja Fajon was "horrified by the death of Navalny". "We lost a tireless freedom fighter. It is absolutely necessary to clarify all the circumstances which caused his death. His fight for freedom and democracy will live forever. My thoughts are with his family and loved ones," she wrote on X.

Russia's most prominent opposition politician died on 16 February in a prison colony in the far north of Russia, where he was serving a 19-year sentence. The cause of death is not known yet, but the West holds the regime of Russian President Vladimir Putin responsible for his death.