The 36-year-old main suspect was arrested in Frankfurt
German police have arrested a Tunisian man suspected of being a recruiter for Islamic State during raids targeting dozens of addresses.
More than 50 mosques, apartments and businesses were raided in the early hours in central Germany.
Police say the investigation was directed against a total of 16 people aged between 16 and 46.
The 36-year-old main suspect was arrested in Frankfurt.
He is believed to have operated as a recruiter and smuggler for IS since August 2015.
And he is being linked to an attack on a museum in Tunis in the same year.
The suspect is also said to have built up a network of supporters to carry out a terror attack in Germany.
Prosecutors say plans for a possible attack were at a very early stage, and no definite target had been chosen.
More than 1,100 police officers were involved in Wednesday's operation.
Peter Beuth, interior minister for the state of Hesse, said the operation had smashed an "extensive network".
"With this operation, we are sending a clear message to radical Islamists in Hesse," he said. "We have the scene firmly within our sights."
On Tuesday, three men were arrested during police raids in Berlin on terrorism-related charges.
Police believe they were planning to travel to Syria or Iraq to train before returning to carry out an attack.