Updated

The European Court of Human Rights ruled on Tuesday that imprisoned Russian oil magnate Mikhail Khodorkovsky's rights were violated after his arrest in 2003, but rejected his contention that the arrest and subsequent trial were politically motivated.

Khodorkovsky, who was 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 ruling from the court in Strasbourg, France, was made on an appeal filed in connection with his arrest and first trial. It ordered Russia pay 24,000 euros ($35,000) in damages for rights violations, including being held in cramped and unsanitary conditions and for extending his pretrial detention without justification.

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. Khosorkovsky as a defendant and not as a simple witness. Therefore, his detention had been unlawful as it had been made with a purpose different from the one expressed," the court said.

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 on that conviction, 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.