Germany's biggest airports are on alert after four suspected terrorists were spotted staking out Stuttgart airport, reports say.
Police are said to be hunting for a son and father from North Rhine-Westphalia and two others seen taking photos of the airport's terminal and grounds, BBC reported.
Details of the suspects were passed to German police by Morocco's secret service, reports say.
This comes a week after a terror attack across the border in France.
Three people were killed by Cherif Chekatt near a Christmas Market in Strasbourg, which is some 150km (93 miles) from Stuttgart.
Police told public broadcaster ARD that security forces were on alert at German airports, while Bild website said warnings had been extended to all 14 major hubs.