Ukraine feels pinch as Russia hikes gas prices
Ukraine has rejected moves by Russia to almost double the price of Russian gas supplies to the country and threatened legal action.
Ukraine's interim prime minister, Arseniy Yatsenyuk, said Moscow's hikes were a form of "economic aggression".
His energy minister said Ukraine would try to negotiate a gas deal but warned that if talks failed, Ukrainians should prepare for Russia to cut off supplies.
Moscow says the price change is due to Kiev's failure to pay its bills.
Russia's state-controlled company Gazprom has raised the cost of gas to Ukraine by 81 per cent, to $485.50 (€354.33) for 1,000 cubic metres, up from $268.50.
The increase comes amid tense diplomatic relations following Moscow's annexation of the Crimean peninsula.
Meanwhile, Ukraine's security service says it has detained a 15-strong armed gang planning to seize power in an eastern province on the border with Russia.
The Security Service of Ukraine said that it seized 300 machine guns, an anti-tank grenade launcher, a large number of grenades, five handguns and petrol bombs.
It said the group intended to mount a power grab in the Luhansk province on April 10 by sowing panic among the local population.
Luhansk and neighbouring provinces have seen active calls for separatism following February's toppling of President Viktor Yanukovych.
Ukraine's pro-European interim government accuses Russia of fomenting secessionist sentiments.