Europe's top human rights court has found Russia guilty of multiple violations of the basic rights of lawyer Sergei Magnitsky who died in a Moscow prison in 2009 after complaining of mistreatment.

According to the European Court of Human Rights (ECHR), Russian officials deprived Magnitsky of adequate medical care while in custody, which led to his death, was badly-treated by prison guards, and was held in overcrowded conditions.

The court said Russia must pay his widow and mother €34,000 ($38,000) after they took up the case at the court in Strasbourg after his death.

The court rejected a complaint that his arrest was ill-founded and argued that authorities had the right to suspect him of tax evasion. However, it said that this did not give them the grounds to keep him in custody for over a year, adding it was "inherently unfair" to continue proceedings after his death.

Magnitsky died in pre-trial detention in November 2009 after he was charged with organising tax evasion — Russia then convicted him posthumously.