The probe follows complaints filed by the main opposition Republican People's Party (CHP) and several individuals that Erdogan referred to Ocalan as "sayin" -- a word meaning esteemed or honorable, but which also doubles for "mister" -- during a radio interview in Australia in January 2000.

Erdogan has categorically rejected the allegations which were first brought up by the CHP last week.

The prosecutor in charge of the probe will decide whether there is need for a full judicial investigation against Erdogan that could pave the way for charges against him, the Anatolia news agency reported.

He would have to ask parliament for permission to carry out such an investigation since Erdogan has political immunity.

Under the Turkish penal code, praising a crime or criminal offender is punishable by up to two years in prison.

Several politicians from the country's main Kurdish party have been indicted or jailed on these charges for referring to Ocalan as "sayin".

Ocalan is the head of the Kurdistan Workers' Party, which has fought for Kurdish self-rule in the southeast since 1984 in a conflict that has claimed more than 37,000 lives.

Considered by many Turks as the country's main enemy, he has been serving a life sentence for treason and separatism as the sole inmate on a prison island since he was convicted in 1999.