SERIES OF PLOTS
According to media reports, Ergenekon is accused of a series of plots to overthrow Prime Minister Erdogan, elected by a landslide in 2002, by stirring civil disobedience that would force the military to intervene.
Engin said legal restrictions made it impossible to unveil further details on the case. An Istanbul criminal court must now rule on whether to accept the indictment.
The case has added to worries in financial markets, which are already unsettled by a case to close the ruling AK Party on charges of anti-secular activities. The Constitutional Court is expect to announce a verdict in that case within three weeks.
Militant secularists dismiss the AK leadership's arguments that it has abandoned its Islamist roots and point to an attempt to allow the wearing of the Islamic headscarf in universities as just one proof of its intentions. They also fear AK is anchoring its position by placing people in places of influence and power in the courts, education, civil service and security services.
Markets were unaffected by Monday's scheduled announcement. The main share index rose 1.6 percent and the lira was firmer.
The secular establishment, which includes the military and judiciary, has long suspected the AK Party of seeking to turn Turkey into an Islamic state, something the party denies.
The AK Party embraces nationalist and centre-right market liberals as well as religious conservatives and has led the country through a period of strong economic growth and into European Union entry talks. It has a huge parliamentary majority.
The military - which has repeatedly criticised the government and considers itself the guardian of Turkey's secular system - has denied any links to the Ergenekon group.
Engin rejected criticism that it had taken more than a year to complete the indictment, saying this was unavoidable given the volume of documents and number of defendants involved.
As widely leaked to the media, the indictment included references to the killing of a judge in a 2006 armed attack on Turkey's top administrative court and to the bombing of a secularist newspaper.
