The court ruled that holding the founder of the outlawed Kurdistan Workers' Party (PKK) in isolation on the island prison of Imrali constituted mistreatment by the Turkish authorities.

Ocalan, who has been behind bars since his capture in 1999 and subsequent conviction for treason, was the sole prisoner in Imrali until the conditions of his detention were eased in 2009.

The court in Strasbourg said Turkey had violated Article 3 of the European Convention of Human Rights which prohibits "inhuman or degrading treatment", over his conditions up until 2009.

The judges also ruled it had violated the convention by sentencing him to life in prison without any possibility of conditional release.