German prosecutors say they're conducting searches in what they indicate is an investigation of suspected plans for a terrorist attack.

The federal prosecutors' office, which handles terrorism cases, said Tuesday that the investigation involves the suspicion of "preparation of a serious, state-threatening act of violence." That description can refer to a terrorist attack.

The office declined immediately to give further details and didn't specify where the searches were conducted, though it said it expected to elaborate later Tuesday.

It wouldn't comment on a report by public broadcaster SWR that prosecutors suspect two men of Tunisian origin may have been planning an attack using two remote-controlled model airplanes. The report cited no sources.