Imprisoned Russian oil magnate Mikhail Khodorkovsky's rights were violated after his arrest in 2003, the European Court of Human Rights ruled Tuesday.

But the court in Strasbourg, France, also rejected Khodorkovsky's contention that his arrest and trial on fraud and tax evasion charges were politically motivated.

Khodorkovsky, Russia's richest person at the time of his arrest, had funded opposition parties and was seen as a potential political threat to then President Vladimir Putin. Supporters have contended his prosecution on charges of tax evasion and fraud was punishment for challenging the Kremlin.

The court's rejection of that contention appears to be a significant setback to efforts of Khodorkovsky's supporters to portray him as a prisoner of conscience. He is due for release in 2016.

The French court's ruling was made on an appeal filed in connection with his arrest and first trial. It ordered Russia to pay $35,000 US in damages for rights violations, including being held in cramped and unsanitary conditions and for extending his pretrial detention without justification.

'The speed with which the investigating authorities had acted suggested they had been prepared for such a development and had wanted Mr. Khodorkovsky as a defendant and not as a simple witness." —European Court of Human Rights

Khodorkovsky was arrested when special forces officers stormed his plane at a Siberian airport. He had been summoned to be a witness in a criminal case and his detention was initially justified for having failed to appear.

However, the court said, within hours of his detention, he was presented with a lengthy list of criminal charges.

"The speed with which the investigating authorities had acted suggested they had been prepared for such a development and had wanted Mr. Khodorkovsky as a defendant and not as a simple witness," the court said. "Therefore, his detention had been unlawful as it had been made with a purpose different from the one expressed."

Last year, Khodorkovsky was convicted in a second trial of stealing oil from his own company, the now-liquidated oil major Yukos. He was sentenced to 13 years, with the sentence to run concurrently with his previous conviction.

His lawyers said on Monday that Khodorkovsky had filed for parole, saying he is eligible for early release since he has served half of his 13-year sentence.