Prominent Russian human rights activists are calling for the early release of jailed oil tycoon and Kremlin critic Mikhail Khodorkovsky.

The activists, in a statement, said Russian law allows Khodorkovsky and colleague Platon Lebedev to seek parole, because they have served half of their eight-year sentences for fraud and tax evasion.

But authorities insist Khodorkovsky, the former head of the giant Yukos oil firm, is not eligible because of a recent prison infraction -- failure to keep his hands behind his back during an exercise period.

Meanwhile the European Court of Human Rights ruled Thursday that Russia violated Lebedev's rights during pre-trial detention. The court ordered Moscow to pay more than $14,000 dollars in damages.

Charges against the two focus on the 1994 privatization of a Yukos subsidiary.

Prosecutors said they were part of a group that illegally won a 20 percent share in the firm.

Both defendants have maintained their innocence, and claim the charges stem from their support of Russian opposition politicians. Lawyers for Khodorkovsky Wednesday accused authorities of trying to keep their client imprisoned until after presidential elections in March.

Some information for this report provided by AP and AFP.