Constitutional change

The arrests are believed to be linked to a purported 2003 plot to discredit the government, in a plan revealed by the Taraf newspaper in January.

The plot, codenamed Sledgehammer, involved bombing two Istanbul mosques and escalating tensions with Greece by forcing Greek jets to down a Turkish plane over the Aegean Sea.

in depth
 

Timeline: Evolution of Turkey's 'deep state'

  Documentation: 'Sledgehammer plot'
  Documentation: 'Cage plot'
  Analysis: Trial exposes Turkey's secret operations 

Scores of officers were arrested over the alleged plot in February in raids that rocked the country.

Recep Tayyip Erdogan, the prime minister, has vowed to put everyone who conspired against the country's democracy on trial.

His ruling party is also engaged in a battle against the country's secular opposition party over a series of amendments to the constitution.

They could pave the way for trials of top military commanders by civilian courts and would make disbanding political parties more difficult.

Hundreds of civilians, retired and active-duty officers are already on trial on charges of an apparently separate coup plot against the government.

They are accused of membership in an alleged terror network called "Ergenekon", an alleged clandestine organisation set up by elements of the country's security services to defend Turkey's secularist foundations.

Opposition leaders claim the coup probes are tinged by politics, a charge
the government rejects.