The two surviving leaders of Turkey's 1980 coup went on trial Wednesday at an Ankara courthouse where judges rejected pleas by the ailing defendants that they should be spared prosecution.

Hundreds of demonstrators, mostly from left-wing political parties, staged a protest in front of the court as the much-anticipated case began amid tight security and only limited access to the media.

However the defendants -- 94-year-old former president Kenan Evren and his co-conspirator Tahsin Sahinkaya -- were both absent due to poor health.

Evren broke his arm in a fall a few days ago at a military hospital in Ankara, where he is recovering from intestinal surgery, a relative told AFP.

The defendants' lawyer, Bulent Acar, argued the court could not try Evren and Sahinkaya, 86, because the 1982 constitution, introduced by the junta after two years of military rule, was still valid and granted it no such power.

The high court judges however rejected the objection, according to the semi-official Anatolia news agency, one of the few media allowed in the trial which should last three days.

The provision exempting the generals from trial was removed as part of a package of amendments adopted in a referendum exactly 30 years after the coup.

The pair face life imprisonment if convicted of committing crimes against the state.

The military, which has long seen itself as the guarantor of secularism in Turkey, staged three coups in 1960, 1971 and 1980 as well as pressuring an Islamist-rooted government to relinquish power in 1997.

But the coup on September 12, 1980, was the bloodiest of them all. Hundreds of thousands of people were arrested, about 250,000 were charged, 50 were executed, dozens more were tortured to death and tens of thousands were exiled.

The trial is seen as the latest chapter in a campaign by Prime Minister Recep Tayyip Erdogan's government against the once unassailable top brass.

The Islamist-rooted Justice and Development Party (AKP) government and parliament are plaintiffs in the case as alleged victims of the 1980 coup.

President Abdullah Gul, a close ally of Erdogan, said Wednesday that the case would pave the way for a "very significant change of mentality" in Turkey society which he said would act as a deterrent against any more coup attempts.

Protesters gathered outside the court expressed their relief that the case had finally been brought before judges. Some carried banners proclaiming that people who resisted the junta would now "have the final say".

One of the protesters, 56-year-old Ali Imer, told how he was arrested on the day of the coup and subsequently tortured.

"I was jailed for four years for membership of a left-wing political party. I had been tortured for 87 days," he said to AFP. "They threatened to rape my wife if I refused to speak. I was given electric shocks."

Several lawmakers also joined the protest.

"This is a landmark case for Turkey's recent history, but it shouldn't be superficial," said Sezgin Tanrikulu from the opposition Republican People's Party (CHP).

"Not only Evren and Sahinkaya, but also those who ordered the torture should be tried."

Emma Sinclair-Webb, Turkey researcher at Human Rights Watch, said the trial offered "an important opportunity to deliver justice for the gross human rights violations that followed the coup -- most notably, mass torture and deaths in custody, which amount to crimes against humanity."

The junta always justified its intervention with the argument that daily clashes between extremist right and left-wing groups were bringing the country to the edge of a civil war.

The decision to put Evren and Sahinkaya on trial was announced in January.

Evren had opted out of public life since his retirement in 1989, spending much of his time painting by the sea.

He became Turkey's seventh president from 1982 to 1989 after the junta's constitution allowed him to formalise his position as head of state.

Plans have been made to enable the two defendants to join the trial through a video-conference from their hospital beds.

Tensions between the fiercely secularist military and Erdogan's AKP have been building for years with dozens of army officers, including a number of other retired generals, landing up in court over alleged coup plots.

Turkey's former army chief Ilker Basbug went on trial last month for an alleged bid to topple the government.