Protesters hold Turkish flags as they gather near a courthouse in Silivri, where a hearing on people charged with attempting to overthrow Prime Minister Tayyip Erdogan's Islamist-rooted government is due to take place on Monday. A Turkish court sentenced retired military chief of staff General Ilker Basbug to life in jail on Monday for his role in the "Ergenekon" conspiracy to overthrow the government of Prime Minister Tayyip Erdogan. Photo: Reuters

Turkey's former army chief, Gen Ilker Basbug, has been sentenced to life in prison after being found guilty of plotting to overthrow the government.

Gen Basbug was among dozens of people convicted in the long-running trial of more than 270 military officers, lawyers, academics and journalists.

They were all accused of involvement in the so-called "Ergenekon" plot.

Verdicts are being read out one by one at the specially constructed courtroom. Twenty-one people have been acquitted.

Gen Basbug, who led the military between 2008 and 2010, had rejected all the charges against him.

The plot allegedly aimed to topple the Justice and Development (AK) Party government.

The defendants faced dozens of charges, ranging from membership of Ergenekon - an alleged underground terrorist network - to illegally possessing weapons and instigating an armed uprising against the AKP.

Prosecutors had demanded life imprisonment for Gen Basbug and 63 others, including nine other generals.

The court is sitting at the high-security Silivri prison complex, west of Istanbul, where the general is being held.

Hundreds of riot police fired tear gas to disperse some 1,000 protesters who were marching outside the courthouse, reports say.

The case is being seen as a key test in Prime Minister Recep Tayyip Erdogan's showdown with secularist and military opponents.

Since Erdogan came to power in 2002, hundreds of military officers - serving or retired - have been arrested.

Critics say there is little evidence for the charges and accuse the government of trying to silence its secularist opponents. Critics have complained that the Ergenekon investigation has focused on opponents of the AKP, which has Islamist roots. The government denies any such motives.

Turkey's military has long seen itself as the guarantor of the country's secular constitution.

It staged three coups between 1960 and 1980 and has a history of tension with the AKP.

The AKP 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.