Alexei Navalny, Russian President Vladimir Putin's most formidable domestic opponent, has died in the Arctic penal colony where he was serving a three-decade sentence,

The death of Navalny robs the Russian opposition of its most prominent leader as Putin prepares for an election this year.

Vigils have been held outside Russian embassies across Europe as western leaders and Navalny's wife Yulia Navalnaya, say that Russia is responsible