(Adds Akhmetov in the capital Kiev)
DONETSK, Ukraine, May 25 (Reuters) - Scores of armed pro-Russian separatists massed outside the walled home of Ukraine's richest man, Rinat Akhmetov, in the eastern city of Donetsk on Sunday as Ukrainians voted for a new president.
The rebels, roundly denounced by Akhmetov, have prevented voting in Donetsk, an industrial hub of a million people, and other parts of mainly Russian-speaking eastern Ukraine, where they have declared "people's republics" outside Kiev's control.
Coal and steel billionaire Akhmetov, whose factories and mines employ about 300,000 people, denounced the rebels last week, accusing them of "genocide", and urged people to vote on Sunday despite intimidation and threats from the separatists.
The 47-year-old, who also owns Shakhtar Donetsk soccer club, was in the capital Kiev when about 200-300 separatists and supporters advanced on his residence, a spokesman said.
"Mr. Akhmetov is today in Kiev. He had intended to return to Donetsk to vote but as you can see from what is happening there and on the streets this has not been possible," said Jock Mendoza-Wilson at Akhmetov's company, System Capital Management.
Some of the men were masked and were aggressive towards journalists as they gathered by the high walls of Akhmetov's suburban residence, which is protected by armed security guards.
Journalists at the scene later said the crowd had calmed down and appeared to be negotiating with representatives on Akhmetov's side though it was not clear with whom. (Reporting by Sabina Zawadzki and Lina Kushch; Writing by Gareth Jones and Richard Balmforth; Editing by Alastair Macdonald)