Two major Ukrainian steel plants were urged to stage a three-hour strike on Tuesday by their owner, billionaire Rinat Akhmetov, who called on them to take to streets to reject pro-Russian separatism.
The strike at Azovstal and Ilyich Iron and Steel Works, both based in Mariupol in the Donetsk region, is due to start at noon local time (0900 GMT) and last three hours.
The strike should be repeated every day until pro-Russian separatists stop intimidating the region, Akhmetov said.
The development underscores serious concerns by Akhmetov, the wealthiest Ukrainian, after pro-Russian separatists took over public buildings and held a controversial referendum demanding independence for the self-proclaimed Donetsk People's Republic.
"I want to tell everyone," Akhmetov said in a statement read on his Ukrayina television late Monday. "We will not stop and we will not be intimidated by anyone who calls himself the Donetsk [People's] Republic. Who has ever heard of it? Who knows its leaders? What did they do for Donetsk?" This is the first statement from Akhmetov clearly denouncing the separatism in the region since Russia has occupied and annexed Crimea, a Ukrainian Black Sea peninsula, in March.
Akhmetov also owns assets in Crimea, including local power distributor DTEK KrymEnergo, power plants and other assets.
Ukraine, the US and the EU said the annexation of Crimea was illegal, while Kiev also blamed Moscow for sending special operations forces to eastern parts of Ukraine, including to Donetsk and Luhansk, to take over government buildings and to destabilize the region.
Moscow denied involvement, but massed 40,000 troops at the border with Ukraine over the past two months.
Ukraine's largest diversified business group SCM, owned by Akhmetov, controls assets in coal mining, steel and steel pipe production, power generation and distribution, energy, finance, telecommunication, media and other sectors of the economy.