Security officials say that a Tunisian asylum seeker arrested on Wednesday morning on suspicion of planning an attack was also wanted by Tunisia over his suspected involvement in the deadly militant assault on the Bardo Museum in Tunis.
A mass operation across central Germany in the early hours of Wednesday morning culminated in the arrest of a Tunisian man suspected of plotting an attack.
A 36-year-old asylum-seeker found in Frankfurt is now under investigation. He's thought to have recruited and trafficked for Islamic State in Germany since 2015, building up a network of supporters to carry out terrorist attacks.
He's among 15 others also being investigated. German police arrested three men in Berlin over suspected links to Islamic State militants, saying they planned to travel to the Middle East for combat training.
Attack plans were at an early stage and no concrete target had been chosen, but prosecutors said the operation had smashed an "extensive network".
The Frankfurt suspect was also wanted in Tunisia where he's thought to have been involved in the deadly militant assault against the Bardo Museum in Tunis.
In Germany, nerves are still on edge after failed asylum seeker Anis Amri killed 12 people by ploughing a truck into a Berlin Christmas market
, the worst of a spate of attacks on civilians in the country.