German authorities are investigating 40 cases in which Islamic militants are suspected of having entered the country with the recent flood of refugees from the Middle East, the federal police said on Wednesday.
That represents a doubling of such cases since January and is likely to deepen concerns about the threat level in Germany, which has not suffered a large-scale Islamist attack like those that have rocked neighbours France and Belgium in recent months.
In the past, the German government has played down the risks of Islamic State fighters entering Europe with the tide of migrants, in part to avoid exacerbating public concerns about the influx, which hit a record 1.1 million last year.
But the head of Germany's domestic intelligence agency Hans-Georg Maassen told a conference last week that although there were more efficient ways to smuggle in fighters, Islamic State appeared to have sent some via the Balkan route from Greece in order to fan fears about refugees and "send a political signal".
"I am not telling you a secret when I say that I am concerned about the high number of migrants whose identities we don't know because they had no papers when they entered the country," Maassen said.
PARIS ATTACKS
The number of migrants entering Germany reached peaks of more than 10,000 a day last autumn, but has fallen dramatically in recent months due to the closing of the Greek border with Macedonia and a deal between the European Union and Turkey that has discouraged refugees from crossing the Aegean Sea.