Gen Ilker Basbug, who retired in 2010, is the highest-ranking officer to be caught up in a widening probe into the so-called Ergenekon network.

Prosecutors say in 2003 the hardline nationalist group tried to bring down PM Recep Tayyip Erdogan's government.

Gen Basbug rejects the allegations. Some 400 suspects are already on trial.

"We can say it is really tragicomic to accuse somebody who commands such an army of forming and directing a terrorist group," Turkey's NTV network quoted Gen Basbug as telling prosecutors.

The Ergenekon trial is one of several involving accusations of anti-government plots by the military and secular establishment.

Some military officers already charged in the case have said they acted in a chain of command.

Turkey's military, the second largest in the Nato alliance after the US, has long seen itself as the guarantor of the country's secular constitution and staged three coups between 1960 and 1980.

But it has a history of tension with Mr Erdogan's governing AK party, with the two sides engaged in a war of words for the past two-and-a-half years over the alleged plots.

Critics have complained that the Ergenekon investigation has focused on opponents of the Islamist-rooted AK. The government denies any such motives.

The AK is considered a successor to the Welfare Party, an Islamist party which led a 1996-97 government forced to resign by an army-led campaign.

bbc.com