Nearly 500 people arrested in the crackdown following the failed July 15, 2016 coup in Turkey will go on trial today. They are accused of conspiring to oust the government from an air base seen as the plotters' hub.

A total of 486 suspects will go on trial in a purpose-built courtroom outside Ankara, charged with crimes ranging from murder, violating the constitution and attempting to kill the Turkish President Recep Tayyip Erdogan, Turkey's state-run news agency Anadolu reported.

They are accused of running the coup bid from the Akinci air base northwest of the capital, which the authorities regard as the headquarters of the plotters where orders were sent out for fighter jets to bomb parliament.

Almost all the suspects — a total of 461 individuals — are held in custody while seven are still on the run and the remainder charged but not in jail.

Among the main suspects named in the indictment but still on the run is United States-based Muslim cleric Fethullah Gulen, who is accused of ordering the attempted July 15 coup. Gulen, who is based in a secluded compound in the US state of Pennsylvania, strongly denies the charges.

Those held in custody include former air force chief Akin Ozturk who, like several suspects, is also on trial in another case related to the coup bid.

'Coup headquarters'

Another chief suspect is theology lecturer Adil Oksuz, whom Turkish officials accuse of being the so-called “imam” of the plot by coordinating the action on the ground in Turkey with Gulen.

Businessman Kemal Batmaz is meanwhile accused of assisting Oksuz.

Oksuz was detained following the coup's defeat, but was subsequently released and is now on the run. Batmaz is in custody in Sincan prison outside Ankara.

Chief of Staff General Hulusi Akar and other senior commanders were held hostage at the base during the coup attempt before they were freed on the morning on July 16.

The base was seen as the coup bid headquarters where commands were given for the F-16 fighter jets to attack and fly them above the capital.

The Turkish parliament was bombed three times by F-16s.

The indictment refers to the suspects' alleged involvement in bombing parliament, areas close to the presidential palace, the special forces' headquarters and the Ankara security headquarters.

The government has suggested the base could be turned into a memorial or park a few weeks after the failed putsch.

Largest courtroom

The trial is taking place in Turkey's largest courtroom established inside a prison complex in Sincan to hear coup-related trials and has space for 1,558 people.

The courtroom has previously hosted mass trials related to the coup bid, including one which opened in February of 330 suspects accused of murder or attempted murder.

And in May, 221 suspects were put on trial accused of being the ringleaders of the failed coup.

The attempted coup left 249 people dead, the Turkish presidency says, not including 24 coup-plotters killed on the night.

Anadolu reported there would be heavy security including 1,130 security personnel inside and outside the courtroom as well as snipers, armoured security vehicles and a drone.

The trial is one of several held across Turkey judging coup suspects, in the largest legal process in the country's modern history.

Over 50,000 people have been arrested over alleged links to Gulen in a wide scale crackdown under the state of emergency imposed following the coup.