US questions Putin's links to oil tycoon Gennady Timchenko

When the US expanded its sanctions to include members of Vladimir Putin's inner circle, one name jumped out - Gennady Timchenko, who rose from obscurity to become one of Russia's richest men.

His Gunvor Group enjoyed a similarly meteoric rise and is now the fourth-largest oil trading firm in the world.

In explaining the sanctions, the US treasury department claimed what others have long suspected. "Timchenko's activities in the energy sector have been directly linked to Putin. Putin has investments in Gunvor and may have access to Gunvor funds," it said.

Gunvor denied the Putin link, calling the allegations "outrageous" and saying: "President Putin has not and never has had any ownership, beneficial or otherwise, in Gunvor." But the personal ties between the two have raised questions.

Like Arkady Rotenberg, another businessman on the sanctions list who has enjoyed success under Putin, Timchenko is an old judo buddy of Putin's.

Forbes magazine estimated Timchenko's wealth at US$15.3 billion, calling him "one of the most powerful people in Russia".

Putin has said he has had nothing to do with the oligarch's business activities. In 2011, Putin said that although he had known Timchenko from when Putin worked in St Petersburg city hall in the 1990s, he "had never meddled" in Timchenko's interests and did not plan to.