Treason appeal rejected in Russia

Sutyagin's trial was the latest in a series of cases against researchers

Russia's Supreme Court has upheld a 15-year sentence against weapons expert Igor Sutyagin, who has been convicted of spying for the US.

In April he was found guilty of passing information to a UK firm that was allegedly a front for the CIA.

Sutyagin has protested his innocence, saying his work was all based on publicly available sources.

Both Russian and foreign human rights advocates have described the case as politically motivated.

Sutyagin, 39, was a researcher at Moscow's prestigious USA-Canada Institute when he was arrested in 1999.

In April he was convicted of passing information on submarines and missile warning systems to a British consultancy.

I absolutely do not consider myself guilty, as I took all information... from newspapers and magazines Igor Sutyagin

He admitted selling information, but insisted that it was readily available and he had no reason to believe the company was run by spies.

The closed-door trial has been criticised in Russia and beyond.

The US state department referred to its "lack of transparency and due process".

Four international rights groups protested to the Council of Europe in January that Sutyagin was "the target of politically-motivated treason charges".

The trial is one of a series of recent high-profile spy cases against Russian researchers.