Based on indications from abroad and international police investigations, prosecutors believe that an Islamist of Arab origin from Berlin is at the head of a group of around 15 people planning the attacks, a statement said.
Earlier press reports said that the suspects were from Russia's troubled Chechnya region. Some of the group are believed to have left Germany to attend extremist training camps in Pakistan, prosecutors said.
The investigation was currently centred on three men aged 28, 30 and 36, prosecutors said. It was unclear if they were in custody, with a spokesman contacted by AFP declining to give further details.
Around 140 police officers were involved in the raids on addresses registered to the suspected Islamists or contact people, seizing computers and various data storage devices.
Prosecutors said that they had no reason to believe there was a link with a series of video threats released ahead of German elections on September 27 that led to heightened security around the country.