Kiev: The pro-Russian rebels in the eastern Ukrainian region of Donetsk want the central government`s troops to withdraw by 9 p.m. Thursday, Miroslav Rudenko, co-chairman of the independent regional government, said.
"Our military forces gave Ukraine an ultimatum yesterday (Wednesday) at 9 p.m. to withdraw its troops ... in a period of 24 hours. If this does not happen, our soldiers could force them to withdraw," Rudenko said.
Donetsk has been at the centre of the pro-Russian uprising against the central government that started in early April.
Pro-Russian fighters have been blocking two Ukrainian units since Wednesday that were deployed in the capitals of the rebel regions of Donetsk and Lugansk.
The two regions declared their independence from Ukraine Monday, a day after holding referendums on political status.
Some 96 percent of voters in Lugansk cast ballots on Sunday in favour of independence, while 89 percent of voters in neighbouring Donetsk backed breaking away from Ukraine.
Pro-Russian separatist leaders in both regions plan to create government entities and military forces, aiming for independent states in the near future as they follow the path taken by Odessa and other regions.
Ukraine`s government leaders said Sunday`s referendum was not valid.
Russia Monday accused Ukraine`s government of using the army to try to scuttle the separatist referendums.
Ukraine`s state-owned Naftogaz gas company, meanwhile, said Thursday it would not pay the $1.66 billion bill that Russian energy giant Gazprom submitted as an advance payment for June deliveries.
"Naftogaz is willing to pay nearly $4 billion" to Gazprom if the price of Russian gas is reduced to $268.50 per 1,000 cubic metres, Ukraine`s acting Energy Minister, Igor Didenko, told reporters.
Moscow eliminated all the discounts it had been giving Kiev following the ouster in late February of pro-Russian President Viktor Yanukovych, pushing the price of gas to $485 per 1,000 cubic metres.
Russian President Vladimir Putin had granted Yanukovych a discount last December that reduced the price that Ukraine paid for natural gas to $268.50 per 1,000 cubic metres.
Polls released Thursday show that businessman Petro Poroshenko is likely to win Ukraine`s May 25 presidential election in the wake of the collapse of support for former prime minister Yulia Tymoshenko.
Poroshenko would win 54.7 percent of the vote, with his support rising by 7 percent to 8 percent since April.
Tymoshenko, who has campaigned actively and travelled to Donetsk, would get 9.6 percent of the vote, according to the polls.
Long-simmering tensions between pro-European western Ukraine and the country`s eastern region, which has close ties with Russia, were exacerbated by the ouster in late February of Yanukovych, a Russian-speaker from the East.
The crisis that led to Yanukovych`s ouster erupted at the end of November, when Yanukovych backed away from plans to ink a pact with the European Union and instead signed a $15-billion financial aid package with Russia.
Brussels`s offer of closer ties with the EU was conditioned on a pledge by Ukraine not to enter into any additional economic accords with Russia, Kiev`s leading trade partner and energy supplier.