Turkish prosecutors have demanded up to three years in jail for Recep Tayyip Erdogan, a rising politician with an Islamic background, for alleged fraud in public tenders, Anatolia news agency reported Friday.

The indictment, the third against Erdogan since May, pertains to a tender held by the Istanbul city council in 1998, when Erdogan was mayor, Anatolia said.

Prosecutors said Erdogan, 48, held responsibility for public damage inflicted by the procedures by approving billboard rents at below market levels.

Recent opinion polls have shown Erdogan's Justice and Development Party would come in first if elections were held now, leading Prime Minister Bulent Ecevit to describe the party as a threat for the country's secular political system, which is staunchly guarded by the powerful military.

The parliament is due to convene on Monday to debate and ratify a plan to hold early elections in November, following a severe government crisis.

The indictment against Erdogan also included charges of fraud regarding a second tender by the Istanbul municipality in 2001, when Erdogan was not in office.

Seventeen other people were charged with offences carrying sentences of between one and three years in jail, Anatolia said.

The date of the opening of the hearing was not known.

Last month prosecutors charged Erdogan with accumulating wealth in unclear circumstances, demanding more than five years in jail for him.

And in May he was indicted for corruption in public tenders, again during his mayorship, for which he risks three to nine years in prison.

Erdogan has spent four months in jail under a 1998 conviction for sedition for publicly reciting a poem with pro-Islamic messages.

The sentence also brought him a political ban, but he argues that it had become invalid under a 1999 amnesty law and some legal reforms.

His eligibility to run for parliament remains a legal controversy.

The charismatic Erdogan, who has in the past denounced Turkey's secular system and its pro-Western orientation, tries to recast himself as a conservative centrist favoring Turkey's integration with the European Union.

Islamist political movements have been under a constant clampdown in Turkey since 1997, when the country's first Islamist Prime Minister Necmettin Erbakan resigned as a result of a harsh army-led secularist campaign.

Erdogan and others among his 53 MPs were members of Erbakan's party, which was later banned for anti-secular activities.AFP