ATHENS, Greece (AP) — Greece's main journalists' union and opposition parties have expressed concern over the arrest of an executive in a small media group for allegedly trying to blackmail the country's defense minister.

The Parapolitika group's manager was arrested in his office Tuesday. The publisher of Parapolitika newspaper also turned himself in to police later.

Defense Minister Panos Kammenos has sued both for libel and attempted extortion.

Kammenos right-wing ANEL party, a junior government partner, said the lawsuit was prompted by allegedly slanderous claims regarding Kammenos' son made during a Parapolitika radio program.

An ANEL statement said the "attacks" were intended to get Kammenos to retract his allegations that the Parapolitika executives had received large sums of improper funding from a state health entity.

The Athens Journalists' Union is urging respect for press freedoms.