- 8 updates
Ukraine's gas debt to Russia will be almost $2 billion if the country fails to pay for February deliveries in full.
Speaking at a press conference, Russian President Vladimir Putin said that Ukraine's current debt stands between $1.5bn and $1.6bn.
Earlier, Russia's top gas producer Gazprom said it would remove a discount on gas prices for Ukraine starting from April.
Russian stock indexes rose at the opening after falling steeply the previous day over fears about the widening international crisis surrounding Ukraine.
Analyst Mark Bradford said a cautious rebound was possible on Tuesday following panic selling on Monday, as there had not been a further significant deterioration in the situation in Ukraine.
The escalating crisis in Ukraine has hit the European markets, which have seen a major slump amid worries the tensions will force higher energy prices if economic sanctions come into effect.
Traders remain wary that a worsening conflict could affect Russia's supply of oil to the EU, two thirds of which is piped through Ukraine.
Oil prices surged by around 2% to above 104 US dollars a barrel in New York while the FTSE 100 Index was off by more than 1.5% at below 6700.
Other leading European markets suffered bigger falls, with the Dax in Frankfurt down by more than 2.5%.
Russia's central bank sold up to $10 billion, or 2 percent of its gold and foreign exchange reserves, to stem the rouble's fall, Moscow exchange dealers have estimated.
"There have been some $11 billion (of foreign currency) sold today, some $10 billion came from the central bank," said Mikhail Paley, a dealer at VTB Capital
The central bank's reserves stood at $493.4 billion, according to the latest data.
Russian Finance Minster Anton Siluanov said on Monday Moscow will decide by the end of the day on financial aid to the Ukraine Crimea region.
The minister did not name a concrete amount of the aid.
"Hysteria" on Russian markets will subside because of Central Bank interventions to support the rouble, but Russia faces a period of strained ties with the European Union and the United States which will weigh on the economy, a senior official said.
"The wave of hysteria will pass, but it is difficult to say when," Deputy Economy Minister Andrei Klepach told Reuters.
"What lies ahead of us is a period of more confrontation and difficulties. For us, that will mean more complicated relations with the European Union, the States, with all the resulting consequences."
Russia's stock markets have dropped about 10% and its currency has fallen to its lowest point ever against the dollar and the euro because of the crisis in neighbouring Ukraine.
The Moscow Exchange fell about 10% in the first hour of trading today, although it later recovered slightly.
The rouble, already down nearly 10% this year, fell below 50 against the euro for the first time. It was trading below 36.4 to the dollar, also a record.