The document is the first to emerge from a year-long investigation into "Ergenekon," a shadowy network of ultra-nationalists and secularists allegedly seeking to topple the Justice and Development Party (AKP) administration.

The investigation has raised political tensions in Turkey, with critics accusing the AKP -- which separately risks being banned for anti-secular activities -- of using the probe to silence its opponents.

The AKP denies the charge.

The 2,455-page indictment includes accusations of creating an "armed terrorist organisation", attempting to use violence to topple the government and provoking an armed uprising, Istanbul's Chief Prosecutor Aykut Cengiz Engin told a news conference.

The indictment, drawn up by a team of three prosecutors, accuses defendants of instigating attacks, including the 2006 bombing of a pro-secular newspaper and an armed attack on a top court the same year that killed a senior judge, Engin said.

Both attacks were initially blamed on Islamist militants, but question marks have been raised subsequently over the real perpetrators.

"The terrorist organization mentioned in the indictment is not a separatist or ideological organisation in the classic sense," Engin said.

He said 48 of the 86 suspects indicted were in custody, but did not say who they were or which charges each of them faces.

The suspects are believed to include at least one former general, nine ex-soldiers, the leader of a small left-wing party and an ultra-nationalist lawyer known for a failed attempt to have Nobel prize-winning author Orhan Pamuk jailed.

Engin said he was legally barred from giving further details on the case, as the indictment must be approved by the Istanbul criminal court to which it was sent before the trial can proceed.

The prosecutor says the charge-sheet does not include 20 other suspects, including two retired four-star generals and a leading Ankara businessman, detained earlier this month as part of the investigation.

A second indictment will be prepared against the latest suspects once prosecutors complete their investigation, Engin said.

The Istanbul prosecutor's office has been investigating Ergenekon since police discovered explosives in an Istanbul house in June 2007.

Media reports said the group was plotting to foment unrest through illegal protests, assassinations and clashes with security forces to provoke a military coup against Prime Minister Recep Tayyip Erdogan's government.

The Turkish military, which has unseated four elected governments in as many decades, is largely distrustful of the AKP for its roots in a now-banned Islamist movement.

The Ergenekon investigation has in turn raised tensions at a time when the AKP is fighting legal action by the country's top prosecutor to have the party banned for undermining the secular system.

Critics note that most of those detained in the "Ergenekon" investigation include opponents of the AKP, and accuse the party of using the probe to retaliate.

But a senior AKP lawmaker on Monday firmly denied this.

"Any government intervention (into the investigation) is out of the question," Bekir Bozdag said. "The government has no authority to direct an investigation. The judiciary is independent."

The AKP denies that it wants to install an Islamist regime in Turkey and says it is fully committed to the separation of state and religion.

But hardline secularists -- among them the army, the judiciary and many academics -- say moves such as easing restrictions on the Islamic headscarf and banning alcohol sales in establishments run by AKP municipalities point to a secret Islamist agenda.

The Constitutional Court is expected to rule in the AKP case as early as next month.