The plot, news of which first surfaced in local media last November, is one of several alleged conspiracies that have strained ties between the secularist military and the ruling AK Party, unsettling investors in the European Union-candidate.
The Sabah daily reported on Tuesday that a newly prepared indictment called for prison sentences for 33 defendants including the three admirals, one of whom is retired, on charges of membership in an armed gang. The other accused include colonels and other officers.
The so-called "Cage Action Plan" allegedly involved bomb attacks and assassinations of non-Muslims, which would be blamed on Islamist militants and used to discredit the government.
State-run Anatolian news agency said the deputy chief prosecutor had sent the indictment to an Istanbul criminal court calling for the case to be merged with another investigation into a cache of weapons found near the city.
The indictment has not been formally released to the public, and details in the Sabah report could not be immediately confirmed.
Dozens of officers, including retired and serving generals, have been charged in recent weeks with plotting to overthrow the government of Prime Minister Tayyip Erdogan.
There is also an ongoing trial of more than 200 people, including retired generals, lawyers and journalists, who are accused of being members of a shadowy far-right group known as Ergenekon and also plotting a coup.
Critics accuse the AK Party government of using the investigations to hound secularist opponents.
The army, self-appointed guardian of Turkey's secular order, has ousted four governments in Turkey since 1960 but its powers have been eroded in recent years by democratic reforms designed to boost the government's bid for EU membership.
The other main pillar of the secularist establishment, the judiciary, is also at odds with the AK Party government, which is suspected by its opponents of harboring an Islamist agenda.
However, Erdogan said late on Monday he did not believe there was an institutional battle going on in Turkey.
"I don't take the view there is a clash between institutions in Turkey. (However) I don't know if there is a clash in the hearts of those who represent the institutions," Anatolian reported him as saying before departing on a trip to London.
His party narrowly survived a bid in the Constitutional Court to ban it in 2008 and is seeking to push through judicial reforms to make it more difficult to ban political parties.
