KIEV/DONETSK, Ukraine, March 1 (Reuters) - A leading telecoms firm and a humanitarian group owned by Ukraine's richest man said on Wednesday they had been forced to stop operating in territory controlled by Russia-backed separatists as their offices had been seized by armed men.
On Monday, separatist leaders warned they would take control of Ukraine-run businesses in rebel-held areas if the government in Kiev did not end a blockade by a group of Ukrainian lawmakers and veterans on rail traffic from separatist territory.
"Our company's office in (rebel-held) Donetsk and equipment have been seized," Ukrtelecom's director, Mikhail Shuranov, said in a post on Facebook.
"The company has cut off the Donetsk sector from the national network," he said. "Around 200,000 of our citizens have lost a means of communication."
Separatist leader Alexander Zakharchenko said rebels were following through on its ultimatum because Ukraine had not lifted the blockade.
"Today since midnight companies have been being taken under external control," separatist website DAN quoted him as saying.
Ukrtelecom is part of a financial and industrial group owned by Ukraine's richest businessman Rinat Akhmetov, whose power-generating and steelmaking businesses on both sides of the eastern front line have already been hit by the blockade's squeeze on coal supplies.
The blockade is a new phase in the three-year stand-off between Ukraine and the pro-Russian rebels that has highlighted the abiding economic ties between the two sides despite a simmering conflict that has killed more than 10,000.
Both the Ukrainian authorities and separatist officials have warned of economic fallout from blocking coal supplies. Separatists say local industrial firms are suffering, while Ukraine says the country could suffer rolling blackouts and lost foreign export income of up to $2 billion.
Russia said the rebels' move to take control of the companies on its territory was partly understandable because the blockade had put the separatists in "an even more difficult situation".
"The steps made by the administrations of these regions, ... can be understood to a degree," Kremlin spokesman Dmitry Peskov told journalists.
A humanitarian group funded by Akhmetov that has been a major supplier of aid to conflict-hit areas also said on Wednesday it had been forced to halt operations in rebel-held areas after distribution points were blocked by armed men.
In rebel-held Donetsk, a Reuters witness saw one police car parked near the fund's distribution centre at a football arena. Signs on the building's doors said the centre was not operating and the entrances had been sealed with papers carrying official-looking stamps, but there was no armed presence.
Ukraine's largest private power and coal producer, DTEK, which is also part of Akhmetov's business empire, said the management of its operations in separatist-held territory had not been taken over.
It was not immediately clear if or how other Ukraine-registered businesses operating in separatist territory had been affected. (Reporting by Alessandra Prentice and Pavel Polityuk in Kiev, Reuters reporter in Donetsk,; Additional reporting by Aleksandar Vasovic in Moscow; Writing by Alessandra Prentice; Editing by Alison Williams)