"It is a lie, Turkey has never stooped so low," said justice minister Cemic Cicek.

He said a group of expert Turkish doctors led by a toxicologist had examined the prisoner, considered public enemy number one in Turkey.

"The results will be made public at the weekend but the allegations made by his lawyers are made up of pure lies," said Cicek, who has previously suggested the claims are intended to provoke international interest in Ocalan.

The rebel leader's defence team on Thursday published the results of tests on his hair, which they said showed probable poisoning by toxic metals.

Ocalan is the leader of the Kurdistan Workers' Party (PKK), which is listed as a terrorist group by Ankara, the EU and the United States but viewed as freedom fighters by many among Turkey's big Kurdish minority.

He has been serving a life sentence for treason and separatism on the prison island of Imrali, where he is the only inmate, since 1999.

Officials from Europe's top human rights organisation, the Council of Europe, have visited Ocalan and said his jail conditions are satisfactory but urged Ankara to ease his isolation.