MOSCOW (AFP) - The Kiev authorities should block the presidential bid of the leader of Pravy Sektor, or Right Sector, movement, Mr Dmytro Yarosh, the Russian foreign ministry's rights envoy said Sunday.

"The de facto authorities in Kiev and their Western protectors must close the road to power for the neo-fascist Yarosh and his supporters," foreign ministry rights envoy Konstantin Dolgov wrote on Twitter.

"The violent mayhem committed by ultranationalists, taking advantage of lawlessness, has completely discredited the Maidan movement," Mr Dolgov added, referring to Kiev's Independence Square protest hub.

Pravy Sektor on Friday announced that Mr Yarosh would stand in elections scheduled for May 25 and said it was ready to go to war with Russia.

The ultra-nationalist group was at the frontline of clashes with police in Kiev.

An ex-Soviet soldier with a degree in Ukrainian literature, Mr Yarosh founded the group in Nov 13 to coordinate radical forces within the Kiev protests.

Russia is seeking Mr Yarosh's arrest on suspicion of calls to commit extremist acts and "terror" in Russia.