Mr Sener is best known for a book that documents the complicity of the police in the 2007 murder of Hrant Dink, a Turkish journalist of Armenian origin.
As Der Spiegel reported last week, veteran journalists Ahmet Sik from the far-left Radikal newspaper and Nedim Sener from the highbrow Milliyet journal were among those rounded up.
Yet even AK's biggest fans worry that the legitimacy of the Ergenekon case is being dented by heavy-handed tactics such as the arrests of Mr Sik and Mr Sener.