* Akhmetov urges employees to join peaceful protest at noon
* Condemns separatists who hold key areas of eastern cities
* Magnate formerly close to ousted president Yanukovich
KIEV, May 20 (Reuters) - Multi-billionaire Rinat Akhmetov, Ukraine's richest man who owns factories across the troubled east, called on his employees to hold peaceful protests on Tuesday in defiance of separatists who plan to disrupt a May 25 presidential election.
In his strongest condemnation yet of the separatists, who have seized strategic points in towns in the heavily industrialised Russian-speaking east, Akhmetov urged people to unite "for Donbass without weapons! For Donbass without masks!"
Akhmetov, a coal and steel magnate who has an estimated 300,000 employees on his payroll, said Ukrainians should stage a "peaceful warning protest" at their companies from noon on Tuesday when sirens would sound across the region.
He said the action should continue daily "until peace is established" and he also urged motorists to join in the protest by sounding their horns.
The sharpness of Akhmetov's attack on the separatists, who he accused of waging a "genocide of the Donbass", appeared to confirm that he was now committed to supporting the efforts of the struggling interim government in Kiev to stabilise the situation in Ukraine with Sunday's presidential election.
Akhmetov, whose fortune is estimated by Forbes magazine at $11.4 billion, is the most powerful single person in the east because of the huge reach of his business empire.
But his full support for the Kiev authorities had been in doubt until recently, given his past association with Moscow-backed president Viktor Yanukovich who was ousted by mass street protests in Kiev in February. Yanukovich has fled to Russia.
Separatist rebellions erupted in the east after the Kiev "Euromaidan" uprising, fuelled by cross-border propaganda from Moscow critical of Kiev's pro-Western authorities. Russia also seized Ukraine's Black Sea peninsula of Crimea.
Earlier this month, Akhmetov's Metinvest company, one of the most powerful in the region, sent miners and metalworkers to the town of Mariupol to join police on patrol, in a further sign the tycoon had decided to enter the political fray.
In his latest statement, issued overnight, Akhmetov sharply attacked for the first time separatists in Donetsk who have proclaimed an independent Donetsk People's Republic (DPR) and have called for it be absorbed into Russia.
"Does anyone in Donbass know at least one representative of this DPR? What have they done for our region? What jobs have they created?
"Does walking around Donbass towns with guns in hands defend the rights of Donetsk residents in front of the central government? Is looting in cities and taking peaceful citizens hostages a fight for the happiness of our region? No, it is not!
"It is genocide of Donbass!," he said. (Writing By Richard Balmforth; Editing by Gareth Jones)