Seven senior military officers have been formally charged in Turkey for allegedly plotting to topple the government in 2003, increasing the number of officers under investigation to 20, the state-run Anatolia news agency said.
They include two serving admirals, three retired admirals and a retired general.
The purported coup plot, codenamed "Operation Sledgehammer", was allegedly drawn up and discussed in 2003 within the Istanbul-based First Army, shortly after the Justice and Development (AK) party came to power.
It was not known whether the suspects made any move to activate the plan, first reported in January by the Taraf newspaper.
The plot allegedly involved plans to bomb mosques and provoke tensions with Greece in a bid to force the downing of a Turkish jet, thus discrediting the government and leading to its downfall.
Other senior military officers have been indicted on charges of planning a separate plot by a far-right group known as "Ergenekon" to overthrow the government.
Also see: Ergenekon: power and democracy in Turkey (openDemocracy)