The former head of Turkey's armed forces, General Ilker Basbug, should be tried in the supreme court if he is charged with plotting to overthrow the government, his lawyer told Reuters.

Lawyer Ilkay Sezer said late on Saturday that Basbug had worked in tandem with Prime Minister Tayyip Erdogan's AK Party government for seven years and he was stunned by the belated accusations against him.

There has been no allegation of a crime until now, that is one and a half years following his retirement ... He says it is beyond his comprehension, Sezer told Reuters.

Sezer said any indictment should be framed by the Supreme Court of Appeals and the case heard by Turkey's top court.

Basbug, military chief of staff from 2008-2010, was sent to Silivri prison, outside Istanbul, on Friday after an Istanbul court ordered he be remanded in custody while the prosecution completed its investigation and prepared formal charges.

Sezer said he was appealing against the custody order.

Military chiefs were once regarded as the most powerful men in Turkey after a series of coups in the late 20th century but since coming to power in 2002 Erdogan's government has introduced reforms that considerably reduced the influence of the generals.

Although hundreds of officers have been detained over the past year suspected of involvement in alleged plots against the government, the action against Basbug stunned many Turks.

There were small pro-military protests in the cities of Bursa, Mersin and Afyon on Saturday, involving a couple of hundred people, according to newspaper reports. The protesters carried Turkish flags and banners that read Not a submissive, but resistant army and Army and people, hand in hand.

The secularist military has a history of tension with the AK due to the party's Islamist roots, although the party shuns the Islamist label and describes itself as socially conservative.

The case against Basbug centres on websites spreading propaganda against Erdogan's government that the military was accused of running until 2008. Several of Basbug's subordinates have been indicted. No formal charges have yet been laid against Basbug.

The retired chief is also accused of leading a gang of anti-government conspirators.

The case is linked to Ergenekon, an alleged ultra-nationalist network police say they first unearthed in 2007. Hundreds of people have been jailed in the investigation, including journalists, academics, lawyers and military officers.

We, and many jurists, claim that if there is a need for a separate indictment, this should be done by the Supreme Court of Appeals and if a trial is required, then it should be held by Supreme Council, Sezer said.

The Constitutional Court also functions as the Supreme Criminal Court to hear cases brought against the country's highest officials for crimes related to their official duties.

One of Erdogan's four deputy prime ministers, Bulent Arinc said on Saturday he hoped the legal process would be speedy and distanced the government from the case.

I hope the court process on Basbug is completed as soon as possible, Arinc said. Nobody has the luxury to commit crimes in Turkey, and the judiciary is independent.

(Reporting by Can Sezer; Writing by Simon Cameron-Moore; Editing by Janet Lawrence)