Istanbul: Turkish ex-Army chief Ilker Basbug on Tuesday rejected terrorism charges against him and refused to mount a defence in his trial for seeking to overthrow the government, the Anatolia news agency said.

"I am astounded at being accused of leading a terrorist organisation," the retired general told a court in Silivri, outside Istanbul, where his trial opened on Monday.

Basbug said the court did not have the jurisdiction to try him, and said he would not present a defence or answer any questions.

"To try and accuse a head of the armed forces of crimes of this nature is the result of a comedy of incompetence," the 68-year-old career soldier said in his first statement to the court.

"The charge sheet has no credibility from my point of view."

Basbug went on trial on Monday on charges of leading a terrorist group dubbed the Ergenekon network accused of plotting to overthrow the government led by Prime Minister Recep Tayyip Erdogan's Islamic-rooted Justice and Development Party (AKP).

Chief of staff of the armed forces from 2008 to 2010, Basbug has been in custody since January and risks life in prison if convicted in a case that has inflamed tensions between the government and the powerful military.

On Monday, the judges rejected a demand by his lawyer for the case to be referred to the Supreme Court.

Critics accuse Erdogan's government of launching the far-reaching probe as a tool to silence its opponents and impose authoritarianism, claims it denies.

Tensions have been building for years between the Army and the Erdogan administration in power since 2002.

The military, which considers itself as the guardian of secularism in modern-day Turkey and is the second-largest force in NATO after the United States, has carried out three coups -- in 1960, 1971 and 1980.

It also forced the removal of a coalition government led by an Islamist prime minister in 1997.

But the Army has lost power following various AKP-implemented reforms, and dozens of active and retired military officers including generals, as well as academics, journalists and lawyers have been detained in the Ergenekon investigation.

A statement issued by relatives of the detained officers has called for the charges to be dropped, accusing the Turkish judiciary of "falsifying evidence".