They are complaining that the police are reading case notes and monitoring their meetings.

They have also asked for protection from crowds at the court house and an end to media leaks.

Lawyer Ahmet Zeki Okcuoglu repeated allegations that police had beaten lawyers with batons after a preliminary Ankara court session on Friday.

He described the incident - which was denied by police - as a "most flagrant violation".

Feeling the heat: Ocalan's lawyer Zeki Okcuoglu in Istanbul

"As defence lawyers we have never been this humiliated," he told an Istanbul news conference.

"We actually wanted to withdraw from this case today," he said. "But we are postponing this decision because we believe our mission could affect Kurdish-Turkish relations."

"If the state does not fulfil these conditions and let us know within a short time ... we will withdraw or suspend our duty as the defence."

Mr Ocalan, the leader of the banned Kurdish separatist group, the PKK, is being held in solitary confinement on a prison island near Istanbul.

His trial is due to begin on 31 May. He faces the death penalty on treason charges.

'Embarrassment for Turkey'

If his lawyers withdraw it could leave Mr Ocalan, if he rejects any state-appointed alternatives, having to conduct his own defence which correspondents say could prove an embarrassment for Turkey.

Mr Ocalan's capture sparked Kurdish protests around the world

The authorities blame the PKK for the deaths of thousands of people during its 15-year campaign for a Kurdish homeland in southeast Turkey.

The rebel leader launched the PKK's armed struggle in 1984. More than 30,000 people have been killed in the fighting. He was arrested in February under an international warrant.

If he is sentenced to death, the far-right Nationalist Movement Party has said it will push parliament to approve the execution, something it has not done since 1984.