Four people, including Yanardag, were detained in Istanbul and Ankara provinces as part of the Ergenekon investigation, the channels said.
The four had worked at Turkish TV channel, Kanalturk, formerly one of the fiercest opponents of the ruling Justice and Development Party (AKP), until the channel was sold to a pro-AKP group in 2008 in a highly debated transaction.
Kanalturk was founded by Tuncay Ozkan, who was detained in the Ergenekon operation last month.
The Ergenekon operation, which started in June 2007 with the discovery of grenades in a house in Istanbul's Umraniye district, is allegedly a crackdown on an illegal organization believed to be planning provoking events that would pave the way for a military coup to overthrow the ruling AKP government.
An Istanbul court began holding the hearings of the case on Oct. 20.
Another indictment would be submitted for those detained in the latest waves of the operation, including two retired generals, journalists, a business group leader and an actress.