Professor Mehmet Haberal owns a pro-secularism TV channel, Kanal B
Turkish police have detained at least 12 people, including a university head, in connection with an alleged plot to overthrow the government, reports say.
Police also searched the headquarters of a television station and offices of groups that promote secularism, the state-run Anatolia news agency said.
The arrests are said to be part of the long-running inquiry into the shadowy ultra-nationalist Ergenekon network.
Its members are accused of plotting attacks to provoke a military coup.
Dozens of people, including retired military officers, politicians, academics and journalists, have been arrested since 2007.
Mehmet Haberal, the president of Ankara's Baskent University, and Fatih Hilmioglu, the former head of Inonu University in Malatya, were among those detained on Monday, Anatolia reported.
The government denies the probe is designed to undermine its opponents
Mr Haberal has in recent months organised meetings with opponents of the governing AK Party, which has its roots in political Islam, reportedly with the intention of forming a new political movement.
He also owns the Kanal B television station, whose headquarters were searched by police on Monday.
Investigators also entered the offices of three non-governmental organisations which took part in mass anti-government demonstrations in 2007, including the Ataturk Thought Association and the Association to Support Contemporary Life, Anatolia said.
Eighty-six people went on trial in October, accused of being part of Ergenekon. Prosecutors say the group is responsible for at least two violent attacks - the bombing of a secularist newspaper in 2006 and an attack on a court in the same year, in which a judge died.
Attacks on those key parts of the secular establishment were supposed to foment chaos and to provoke Turkey's military into launching a coup in defence of secular interests, it is alleged.
The suspects deny the charges, saying they are politically motivated.
Prime Minister Recep Tayyip Erdogan has rejected suggestions that the investigation is designed to undermine the AK Party's opponents.