Oil magnate Mikhail Khodorkovsky is widely assumed to be Russia's wealthiest tycoon by far.

At barely 40, he is credited with a personal fortune of billion - equivalent to the annual GDP of Iceland.

In recent weeks he has become increasingly caught up in a campaign launched against the company he heads, Yukos.

The oil giant has been the focus of inquiries which Mr Khodorkovsky - an open critic of President Vladimir Putin - says are politically motivated.

Analysts believe his troubles may be linked to his stated intention to fund political opponents to Mr Putin in the run-up to parliamentary elections in December.

The Yukos chairman supports two opposition parties, Yabloko and the Union of Rightist Forces.

He has been taken in for questioning twice in recent months in connection with allegations of fraud and tax evasion.

The investigation began in July with the arrest of Platon Lebedev, a top Yukos shareholder, on charges of theft of state property during the 1994 privatisation of a fertiliser plant.

That arrest was seen as a clear warning to Mr Khodorkovsky not to meddle in the upcoming elections.

Mr Khodorkovsky insists Yukos does not back any political group.

"Large companies cannot finance political parties as their shareholders and employees have different political views," he told reporters last month.

However he has made no secret that he supports the liberal opposition to President Putin.

"Ideologically I am close to the Union of Rightist Forces and Yabloko, and I continue to finance these parties," he said.

In September he acquired the rights to publish the prestigious Moskovskiye Novosti newspaper, and hired a leading investigative journalist and Putin critic as editor.

Mr Khodorkovsky began his career as a loyal Soviet-era Communist Party member.

In 1987 - four years before the fall of the USSR - he founded what would become Menatep bank, in which he still has a large stake.

Mr Khodorkovsky made his first millions in the early 1990s, when the bank acquired massive amounts of shares in companies that were privatised for bargain prices.

Mr Khodorkovsky bought Yukos at a state auction in 1995 at the knockdown price of 0m.

He now owns 36% of the shares, while Menatep holds another 60%.

He was one of the first Russian tycoons to openly declare his fortune and took 26th place in Forbes magazine's list of 476 billionaires published earlier this year.

Yukos recently completed a merger with another Russian oil producer Sibneft. The new company, YukosSibneft, is set to become the world's fourth largest private oil producer.

But analysts say it is Mr Khodorkovsky's political activism, not his wealth, that seems to attract the Kremlin's ire.

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