Five generals and an admiral were among a group of soldiers who appeared before prosecutors Friday to answer questions over an alleged 2003 coup plot, Anatolia news agency reported. They were summoned as part of an expanding probe into \"Operation Sledgehammer\", an alleged plan to overthrow the Islamist-rooted government, which has already landed some 200 soldiers in court and fanned political tensions in Turkey, Anatolia said. There were conflicting reports about how many soldiers in total had been summoned for questioning. Four-star general Bilgin Balanli -- head of Turkey\'s military academies and in line to become air force commander this year -- was reportedly on the list. The NTV news channel initially said he was among the soldiers who arrived at the courthouse in Istanbul Friday, but later withdrew the report. Following the questioning, the prosecutor may either press charges and ask judges to arrest the soldiers, or let them go. The trial in the case opened in December with 196 defendants, among them senior commanders. Most of them remain in prison. The investigation however expanded after more documents related to the case were found in the home of a retired colonel in February, NTV said. The probe, the toughest challenge yet to the once-omnipotent Turkish army, has been marred by serious doubts over the authenticity of some implicating documents, fuelling mistrust between the staunchly secularist army and the government. Media reports say the army\'s annoyance over the expansion of the probe might be behind its surprise decision Tuesday to cancel two major military exercises without explanation. The case has landed some 30 generals, about a tenth of the total, in jail, humbling the military after its ouster of four governments in the past. Prosecutors argue the coup plan was drawn up shortly after the Justice and Development Party (AKP), the moderate offshoot of a banned Islamist movement, came to power in November 2002 amid fears it would undermine Turkey\'s secular system. The soldiers allegedly plotted to bomb mosques, and down a Turkish jet over the Aegean and blame it on Greece, hoping to discredit the AKP and garner public support for a coup. The alleged mastermind, retired general Cetin Dogan, says papers from a seminar on a contingency plan based on a scenario of tensions with Greece and domestic unrest have been doctored to look like a coup plan. About 300 other suspects, among them soldiers, journalists and intellectuals, have been charged since 2007 as part of several cases that emerged from another sprawling probe, targeting an alleged terrorist organisation called Ergenekon. Prosecutors argue Ergenekon plotted to lay the ground for a coup through strategies ranging from media propaganda and street protests to bombings and assassinations. Also Friday, an Istanbul court approved an indictment against 10 people in a new case, and scheduled the trial for August 23, Anatolia reported. Admiral Kadir Sagdic, already detained as part of the \"Sledgehammer\" probe, was among five defendants who risk a life sentence on charges of attempts to overthrow the government, it said. The prosecutors also seek jail terms ranging from one to 45 years for the 10 defendants, it said. The case resulted from the seizure of allegedly incriminating papers from a navy base in Golcuk, western Turkey, in December, followed by the discovery of explosives and bullets in a dig in an Istanbul suburb. Some of the suspects were accused also of links to Ergenekon, Anatolia said.