A Turkish prosecutor has launched an investigation into an ultimatum the armed forces gave to the moderate Islamic government almost five years ago, newspapers reported Thursday.

A specially authorised prosecutor in Ankara acted on various complaints about the statement penned by then chief-of-staff retired General Yasar Buyukanit, now 71, said the Hurriyet and Radikal dailies.

At midnight on April 27, 2007 the military -- which considers itself the guardian of secularism in modern-day Turkey -- issued an online memorandum that was seen as openly interfering in politics.

The statement, sometimes dubbed the 'e-memorandum' or 'e-coup', said the armed forces were following with concern a debate about secularism in the midst of an election campaign to nominate the next president.

The statement, issued at a tense political time, threatened to intervene to protect the secular camp being denounced in demonstrations by the Justice and Development Party (AKP) of Prime Minister Recep Tayyip Erdogan.

At the time, parliament in a vote boycotted by the opposition elected foreign minister Abdullah Gul, an AKP member, as president. Shortly after, a referendum ratified a constitutional amendment championed by the AKP for the head of state to be elected by popular vote.

Buyukanit, who has admitted writing the memorandum, and key commanders who were serving at the time, could soon be summoned to court, said the reports.

The case will be handled by the same prosecutor who recently charged the chief of the junta that seized power in a 1980 coup, said the Hurriyet daily.

Two retired generals, Kenan Evren and Tahsin Sahinkaya, are set to appear on April 4 before an Ankara court charged with crimes against the state, which is punishable by life imprisonment.

Evren came to power after the coup and was Turkey's seventh president from 1982 to 1989. Five army generals took power in 1980 but Evren and Sahinkaya are the only ones who are alive today.

The two will be the first coup leaders to face trial in Turkey, where the army was once untouchable and toppled four governments since 1960.

The military's powers have been sharply reduced in recent years by reforms implemented by the AKP.

Dozens of officers are now in jail, charged in various alleged plots against the government that has been in power since 2002.

Ilker Basbug, who was army chief from 2008 to 2010, has also been arrested for an alleged bid to topple the government.

He is the most senior officer implicated in an investigation into the so-called Ergenekon network of dozens of active and retired military officers, academics, journalists and lawyers.