By Helen Fawkes
BBC News, Kiev
Russian prosecutors have cancelled an arrest warrant for the former Ukrainian Prime Minister Yulia Tymoshenko.
Yulia Tymoshenko has agreed to co-operate with the investigation
The decision was made after she went to Moscow voluntarily to give evidence to the military prosecutor's office and agreed to return for the investigation. Mrs Tymoshenko was appointed prime minister after playing a leading role in Ukraine's Orange Revolution.
The mass protests led to Ukraine getting its first pro-western president, Viktor Yushchenko.
During her time as prime minister, Yulia Tymoshenko had refused to travel to Russia because of the arrest warrant but on Saturday she made a private visit to Moscow.
Mrs Tymoshenko is accused of bribing Russian military officials when she was in charge of Ukraine's main gas distributor in the 1990s, an allegation she denies.
Now the arrest warrant, which had strained relations between Ukraine and Russia, has been lifted.
The timing of this is seen as significant - it was less than three weeks ago that the prime minister was sacked.
She has vowed to stand against the president's party in next year's parliamentary elections in Ukraine.
Analysts say that Mrs Tymoshenko is changing her political image to make her more attractive to pro-Russian voters.
The former prime minister has not yet commented on the situation but is expected to appear live on Ukrainian television later on Monday.