All the evidence from the last 12 months shows that the danger of terrorism posed by refugees “is not larger or smaller than that in the rest of the population”, Altmaier told broadcaster ZDF.

The chief of staff was making the comment after a 17-year-old who had arrived in Germany in 2015 claiming to have fled from Afghanistan, attacked passengers with an axe on a train near Würzburg, seriously injuring four people.

Investigators believe it is very likely that there was a religious motive to the attack, as the teenager was heard to shout “Allahu Akbar” (God is great) on several occasions.

The terror group Isis has also released a video which purports to be of the attacker in which he makes threats in Pashto while holding a knife. 

“Most of the terrorists who have carried out attacks in Europe over the past few months were not refugees, they were people who were born here and who grew up here,” Altmaier said.

Others travelled here on official tourist visas, he added.

He also maintained that it is obvious that when so many people arrive in Germany as refugees “the one or the other is also susceptible to these types of ideologies.”

Altmaier, one of Merkel’s most trusted confidants, said that German security services are already carefully checking information about refugees who arrive in the country against data banks which already exist on refugees.

But the axe attacker in Würzburg had never appeared on the radar of security services either before or after he fled his home, said Altmaier.

In 2015, Germany accepted several hundred thousand asylum seekers from several predominantly Muslim countries. The highest number came from Syria, but tens of thousands also arrived from Iraq, Afghanistan and Pakistan.