* Far-right leader seeks presidency in Ukraine
* Russia portrays Ukraine's leaders as radical nationalists
By Lidia Kelly
MOSCOW, March 9 (Reuters) - A senior Russian official appealed to the West on Sunday to help prevent "neo-fascists" coming to power in Ukraine after a far-right leader said he planned to run for president.
Dmytro Yarosh, leader of the Right Sector paramilitary movement which played a big role in three months of protests that toppled Ukraine's Moscow-backed president, announced his candidacy for the May 25 election on Saturday.
"The de-facto authorities in Kiev and their Western backers should close the road to power of the neo-fascist Yarosh and his supporters," Konstantin Dolgov, the Russian Foreign Ministry's human rights commissioner, said on Twitter.
Moscow has charged Yarosh with incitement to terrorism for allegedly suggesting a Chechen warlord should attack Russia after Russian forces took control of Ukraine's Crimea region.
Political analysts in Ukraine say Yarosh is a rank outsider in the election because of his ultra-nationalist views.
President Vladimir Putin has said that Ukraine's new leaders seized power in an unconstitutional armed coup and that Russia has the right to invade Ukraine to protect Russians living in the former Soviet republic.
Russian officials tar other protest leaders with the same brush as Yarosh, and portray the Ukrainian leadership as radical nationalists backed by the West. Russian state media have widely repeated the accusations.
Moscow also blames the protesters for clashes in which Ukraine's Health Ministry says about 100 people were killed.
The dead included police but witnesses said the vast majority were protesters killed when riot police charged or attacked them, and that some were killed by sniper bullets.
"The violence of the ultra-nationalists who have been enjoying impunity has completely discredited Maidan (the protest movement)," Dolgov said. "Militants guilty of murder should be brought to justice."
Yarosh on Saturday described Moscow as the aggressor following Russian forces' intervention in Crimea and said Ukraine was "in a state of war with Russia".
(Editing by Timothy heritage)