He was one of 16 people arrested across the central state of Hesse, as 1,100 police searched flats, businesses and mosques.

The man is also wanted by Tunisian authorities over a jihadist attack on the Bardo Museum in Tunis.

Twenty-one tourists and a Tunisian were killed in March 2015.

Many of the victims were British, Japanese, French, Italian or Colombian.

Authorities in Frankfurt said Wednesday's operation was the result of a four-month investigation. They had evidence Islamists were preparing an attack, but described the planning as in its early stages.

Those arrested are aged between 16 and 46 and are suspected of helping a foreign terrorist group and of planning serious violence.