This was confirmed by a spokeswoman for the Civic Council, a group that recruited the activist.

A popular opposition activist in Russia, Ildar Dadin has lost his life while fighting in Ukraine on the side of Kyiv, BBC reports.

This was confirmed by a spokeswoman for the Civic Council, a group that recruited the activist.

The group described him as a hero, saying “he was, and he remains a hero” for standing firm against Russian oppression until his last breath.

The activist-turned-fighter was slain when men from his volunteer battalion, the Freedom of Russia Legion, were targeted by Russian artillery in the Kharkiv region of northeastern Ukraine.

No additional information is available for the time being, and the Legion will not comment while a military action is ongoing.

However, Ilia Ponamarev, an exiled Russian opposition figure with historical links to the Legion, confirmed his death to the BBC.

Another account added that this was “confirmed by those who were with him in battle”.

Dadin rose to prominence in Russia a decade ago for his persistence in organising peaceful protests despite increased political repression.

He was the first person charged under a new Article 212.1, sometimes known as Dadin’s Law, which made repeated infractions of Russia’s increasingly draconian protest restrictions a criminal offence in 2014.

Dadin was sentenced to two and a half years in prison and went on hunger strike shortly after being placed in a punishment cell. His prison guards then tortured him to force him to stop.