LONDON, July 8 (Reuters) -- Russian billionaire Roman Abramovich has placed a bid for a stake in Rosneft, giving a boost to the Russian oil group's planned initial public offering, the Financial Times newspaper said on Saturday.

The newspaper, citing unidentified people familiar with the details, said Abramovich made the bid earlier this week. It was likely to have been for several hundreds of millions of dollars worth of shares, it said.

Rosneft, Russia's most leveraged firm, is planning to raise $11 billion from an initial public offering of between 13 and 19 percent of its stock in London and Moscow on July 14.

The Financial Times said a spokesman for Abramovich declined to comment. An Abramovich spokesman contacted by Reuters also declined comment.

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