A German-Moroccan couple was arrested Thursday in central Germany on charges they were planning an Islamic extremist attack. A series of raids included searches of the homes of 12 other suspects, Frankfurt prosecutors said.

Frankfurt prosecutor Nadja Niesen said authorities believe the suspects were in the early stages of planning an attack in Germany.

"There was not yet a concrete attack target that we're aware of," she said.

The couple, both 26 and German-Moroccan dual nationals, tried to travel with their two young children to Syria in 2016 to join the Islamic State extremist group, but were captured in Turkey and deported back to Germany, Niesen said.

They were arrested at their home in the Raunheim area, southwest of Frankfurt in the state of Hesse. Overall, some 200 police officers raided 15 homes in Ruesselsheim, Biebesheim, and Raunheim in Hesse as well as one in Kerpen in North Rhine-Westphalia

The nationalities of the other suspects were given as either German or German-Moroccan. The 12 were between 22 and 33 years old and face charges of accessory to planning an attack in Germany, Niesen said.

No names were released in line with German privacy regulations.