Several high-ranking Turkish ex-officers were arrested on Monday on suspicion of being behind the 1997 forced removal of an Islamist-led government, local media reported.
Among them is Cevik Bir, a four-star general widely seen as having been the mastermind of the 1997 events, according to the Anatolia news agency.
Bir was number two in the army chiefs of staff in 1997, the last time Turkey's once all-powerful military was involved in changing the government when it forced out a coalition led by an Islamist prime minister.
The arrests came after police searched the homes of former army officers as part of the probe, one of several investigations that have heightened tensions between the current Islamist-rooted government and an increasingly weakened military.
The 1997 events are often referred to in Turkey as a "post-modern coup" as unlike previous putsches it involved no troops and the deposed cabinet was not replaced by a military regime.
Tensions have been rising for years between the military, which sees itself as the guardian of secularism in modern-day Turkey, and the government of Prime Minister Recep Tayyip Erdogan and his Justice and Development Party (AKP), in power since 2002.
In addition to the investigation of the 1997 events, dozens of active and retired military officers including generals, as well as academics, journalists and lawyers have been detained in the so-called Ergenekon probe.
Authorities say the investigation targets a terrorist group accused of plotting to overthrow Erdogan's government, but critics accuse Ankara of launching it as a tool to silence its opponents and impose authoritarianism, charges it denies.
April also saw the start of the trial of the leaders of the 1980 military coup, the first time in Turkish history that the perpetrators of one of the nation's three coups have faced justice.
The Turkish military, which has seen its power wane following various AKP-implemented reforms, carried out coups in 1960, 1971 and 1980.
