The biggest trial of suspects accused of involvement in last year's failed July coup opened in Turkey on Tuesday in a courtroom specially built to hold more than 1,500 people.

Some 330 suspects are being put on trial in Sincan outside the capital Ankara, and if convicted, they face multiple life sentences over their alleged links to the attempted overthrow of President Recep Tayyip Erdogan.

Over 240 of those named in the indictment are in custody, state-run news agency Anadolu reported.

The suspects, many of them from the Polatli artillery and missile school command in Ankara, have been charged with murder or attempted murder.

They also stand accused of attempting to remove the government and parliament of the Turkish republic or trying to prevent those institutions from conducting their work.

The case is being heard at Sincan prison where there was heavy security in place, with a water cannon truck on site and a drone flying overhead as families arrived for the hearing.

The courtroom — which has space for 1,558 people — was packed with security forces surrounding the suspects as they testified.

'Be prepared'

The first suspect, a military cadet called Abdulkadir Kahraman, told the court that on the night of the coup, troops had been informed by their commander that there had been a terror attack and were given ammunition.

Other suspects gave similar statements, including Arif Ozan Demir who told the court the commander told them there had been an attack and that they should “be prepared”.

Ankara has blamed the failed putsch on Islamic preacher Fethullah Gulen — who lives in self-imposed exile in the United States — and his movement.

Turkey has denounced the movement as a terrorist organisation and the suspects on trial at Sincan are also accused of belonging to an armed terror group.

The hearing is one of several cases that opened across the country this month, with 47 people going on trial in the western city of Mugla on charges of attempting to assassinate Erdogan.

Until now, the largest had been in the Aegean city of Izmir where 270 suspects went on trial late last month, among them Gulen who was being tried in absentia.

Following the failed putsch, Ankara declared a state of emergency and began a widespread crackdown, placing more than 43,000 people in pre-trial detention.

The state of emergency remains in place as the trials get under way in the biggest legal process in the country's history.