Colonel Dursun Çiçek was arrested on Wednesday on suspicion of "membership of a terrorist group". Çiçek is regarded as the author of the plan targeting the government and an Islamic movement. He has denied the charge. Çiçek had been detained previously over suspected links to a separate plot to overthrow the government by a shadowy, nationalist group known as "Ergenekon". A trial on that alleged coup plot is under way.
Army suspicions that Erdoğan's AK Party has a hidden Islamist agenda and aims to undermine the country's staunch secular order have repeatedly triggered political strains in recent years, unsettling financial markets. The AK Party denies having such an agenda.
A plot to discredit the government was first unveiled in June by liberal newspaper Taraf, which said it had obtained a photocopy of a document drafted by Çiçek detailing the plan. The military said the document was a forgery and part of a smear campaign. It opened another investigation after newspapers reported an unnamed officer sent the original document of the suspected plot to a prosecutor. The military, which has ousted four governments in 50 years, has said it is committed to the rule of law.