A Russian opposition activist who is in prison after being convicted of assaulting police during a protest has started a hunger strike.

Rights activist Yelena Efros told Ekho Moskvy radio on July 24 that Sergei Mokhnatkin is protesting the failure of administrators of the prison in the remote northern town of Kotlas to provide him with adequate medical care.

Mokhnatkin, 63, was sentenced to 4 1/2 years in prison in 2014 after being found guilty of assaulting two police officers during a December 2013 antigovernment protest in Moscow.

He says prison guards beat him severely in March 2016, damaging his spine, after he refused to be transferred from one facility to another without a written ruling.

Mokhnatkin was charged with insulting a guard and disrupting prison operations and in March 2017 was sentenced to two additional years.

Mokhnatkin first came to prominence in 2009 when he was sentenced to 2 1/2 years in prison after being convicted of attacking a police officer during another opposition rally. He was pardoned by then-President Dmitry Medvedev in April 2012, one month before Vladimir Putin returned to the presidency.

With reporting by Ekho Moskvy