Irfan Dundar, speaking on behalf of all lawyers representing Ocalan, told a press conference here their client, who was jailed in 1999, had been sanctioned with a 20-day-long confinement in a cell, a disciplinary measure which bars him from meeting his lawyers.

A group of lawyers planning to visit him last week were prevented from travelling out to the Imrali prison island for that very reason, Dundar said.

"We believe it necessary to underline that this new illegal and arbitrary practice which Ocalan has been subjected to... is a decision that could lead to very serious social tensions and conflicts," Dundar said, reading out a press statement undersigned by several pro-Kurdish associations.

Dundar called on authorities to release information on the health and welfare of Ocalan, whom they have not been able to meet since November 30.

Ocalan, the leader of the outlawed Kurdistan Workers' Party (PKK), was sentenced to death in 1999 for his role in his group's bloody armed campaign for self-rule in Turkey's mainly Kurdish-populated southeast.

His sentence was commuted to life in prison in 2002 after Turkey abolished capital punishment as part of reforms to boost its bid to join the European Union.

Last year, Ankara introduced restrictions on Ocalan's meetings with his lawyers, whom it accused of carrying orders from the rebel leader to his militants who have recently stepped up their armed campaign.