The trial opened on Monday of almost 50 suspects accused of plotting to assassinate Turkish President Recep Tayyip Erdogan at a luxury Aegean hotel on the night of the botched July 15 coup.
Forty-four suspects, mainly soldiers, are under arrest, while three others still on the run are being tried in absentia at the court in the southern city of Mugla.
The suspects, several smartly dressed in suits and ties, were led into the court by security forces in front of television cameras, AFP correspondents said.
Onlookers heckled them as they stepped out of the buses that took them from prison, shouting "we want the death penalty!" and "Allahu Akbar" ("God is Greatest").
Erdogan, who was holidaying at a hotel in the upmarket Aegean resort of Marmaris with his family on the night of the coup, has said the plot left him 15 minutes from death.
Prosecutors have sought multiple life sentences for each of the suspects, who include an alleged hit squad of 37 soldiers suspected of seeking to carry out the plan.
The trial was taking place under the highest security with snipers posted on rooftops and helicopters circling overhead.
It is being held in a conference centre rather than a standard courtroom to accommodate the high number of suspects.
Turkish officials say the plot to kill Erdogan was a key part of the plan to depose the elected government, a scheme they say was masterminded by the US-based Muslim cleric Fethullah Gulen and his so-called Fethullah Terror Organisation (FETO).
The plan was to "neutralise the president," Erdogan's lawyer Huseyin Aydin told AFP outside the court.
"If our president was neutralised as planned, the course of the coup would have been different. We would have been faced with a different Turkey," he said.
Ankara has repeatedly demanded that the United States extradite Gulen, who lives in a secluded compound in the US state of Pennsylvania.
The preacher, who is on trial in several cases in Turkey, is one of the three suspects still at large in the assassination plot trial.
Onlookers waving Turkish flags chanted slogans against the accused and Gulen, including "Execution!" and "Game Over, FETO".
After the coup, there have been calls to reimpose the death penalty in Turkey, which was abolished in 2004. Its reinstatement would spell the end of Turkey's embattled bid to join the European Union.
Despite this, Erdogan has repeatedly told crowds at rallies he would approve legislation reimposing the death penalty if it was approved by parliament.
Getting the trial underway, judge Emirsah Bastog said the initial phase would last until March 15, with more hearings in April and then in June.
Inside the tense court, suspects were placed at the centre surrounded by dozens of soldiers with batons.
Accompanied by close family members including his son-in-law, Energy Minister Berat Albayrak, Erdogan managed to flee Marmaris and fly to Istanbul where he oversaw the suppression of the coup.
"If I had stayed 10 or 15 additional minutes there, I would have been killed or I would have been taken," Erdogan told CNN in an interview on July 18.
Two Turkish policemen who were helping to guard Erdogan at the hotel were killed, according to the indictment.
Some 43,000 people have been arrested following the coup attempt in a massive crackdown on followers of Gulen that has raised international concerns.
Gulen vehemently denies being behind the plot.
The Mugla trial is one of many now getting underway across the country to judge the coup suspects, the biggest legal process in the country's modern history.