According to official estimates, some 680 people have left Germany to join militant groups operating in Syria and Iraq, a third of whom are feared to have returned. The country's parliament made it illegal last month for Germans to travel abroad and join terrorist organizations.
"Of course there is a resource bottleneck… We are at our limits," BKA chief Holger Munch told the German DPA agency in an interview.
Citing 500 investigations underway against 800 suspected Islamists, the German police chief said the remaining 300 individuals under surveillance put a strain on the security forces.
He called for a nationwide "master plan" in its anti-terror campaign in the wake of the latest events in and around Germany.
A late April police raid near Frankfurt foiled a terror plot by a married couple, who were found hiding a homemade bomb, an assault rifle, explosives and ammunition in their apartment.
Earlier this year, a string of fatal attacks in the French and Danish capitals staged by self-proclaimed Islamists has put Germany and other European cities on high alert.
