Two jailed members of Russian punk collective Pussy Riot have taken a step closer to freedom after judges at the country's Supreme Court granted them an appeal.

Maria Alekhina and Nadezhda Tolokonnikova are serving two-year sentences for hooliganism over a protest against President Vladimir Putin in a case which has become a cause celebre for human rights campaigners.

The pair has been fighting a lengthy appeal process through Russia's judicial system, and judges at the Supreme Court this week (beg09Dec13) ruled there are question marks over the original case.

The panel confirmed the original trial judges overlooked possible mitigating circumstances including the lack of proof that the two women deliberately set out to offend a specific social group with their protest song performance.

Both of the jailed women are mothers, and the Supreme Court also ruled the trial judges should have considered deferring any punishment because of their family circumstances.

In their judgement, the Supreme Court panel also writes, "Furthermore, the court neglected to take into account several other considerations of significant importance for passing a fair verdict, namely, the defendants' young age, the opinion of the injured parties who did not insist on a harsh punishment, the marital status of Tolokonnikova and Alekhina, their living conditions, as well as the non-violent nature of their unlawful acts."

An appeal hearing is unlikely to take place before next year (14).

Alekhina and Tolokonnikova are due for release in March (14). A third Pussy Riot member, Yekaterina Samutsevich, was freed in October, 2012 when her sentence was commuted.

The pair is hoping to be freed by the end of the year (13) as part of an upcoming amnesty for prisoners convicted of non-violent crimes.