The raids on Koza-Ipek Media sparked fresh concern about deteriorating press freedoms in Turkey, which is gearing up for a snap November legislative election, its second in five months.
Six people have been arrested and an arrest warrant has been issued for the conglomerate's chief executive, Akin Ipek, who is thought to be in Britain, the state-run Anatolia news agency said.
The swoop came a day after a court in Turkey's Kurdish-dominated southeast ordered two British journalists working for US-based Vice News to be remanded in custody on "terror charges".
Masked police entered 23 offices as well as Ipek University in Ankara belonging to its parent company Koza Ipek Holding "as part of a terrorist investigation into Fethullah Gulen", Anatolia said.
They were accused of "providing financial support to and disseminating propaganda for a terrorist organisation," Anatolia added.
Speaking live to Kanalturk on Tuesday, Ipek denounced the operation as "baseless" and "funny", adding: "If they (police) are able to find even a cent of illicit money, I am ready to hand my company over to them.
