Airports across Germany were under heightened security on Friday amid concerns over a suspected terror plot.
Heavily armed police patrolled Stuttgart airport after two men were filmed on closed circuit cameras behaving suspiciously and taking photographs of a security gate on two separate occasions in the past week.
The two men, who are believed to be Islamists known to German police, were also filmed behaving suspiciously at Paris’ Charles de Gaulle airport last week.
Police in Germany raided three apartments on Friday morning as prosecutors confirmed they are investigating four people on suspicion of planning a serious act of violence.
Horst Seehofer, the German interior minister, said he did not want to alarm people but called on the population to be vigilant, adding that it was “the best form of prevention against terror attacks”.
“Security is increased at all airports. But we do not have any information concering airports other than Stuttgart and in France,” Mr Seehofer told reporters. “Besides, it would be unwise to talk too much about it.”
Authorities in Germany have been tight-lipped about the exact nature of the threat, but details leaked to the German press suggest that the investigation centres on a father and son of Moroccan descent living in the city of Aachen, close to the French border.
The older of the two men is a 48-year-old imam known to German police as an Islamic extremist.
The two men were first noticed behaving suspiciously at Charles de Gaulle airport last week. They escaped before French police could stop them but authorities were able to trace them by the German license plate on their car.
The two men were next filmed at Stuttgart airport, where they did not board an aircraft but took photographs of a security area.
Two others are also under investigation in connection with the case. One is understood to be a friend of the imam’s son.
German investigators are reportedly in possession of online messages sent by the men intercepted by Moroccan intelligence.
Security has been stepped up at all German airports according to Mr Seehofer, but it is most visible at Stuttgart and other airports in south-western Germany, where police wearing body armour and carrying machine-guns are patrolling the departure area.
Flights have not been affected and there is currently no indication of any link to the drone chaos at Gatwick.