GETTY German Chancellor Angela Merkel (R) chats with CDU faction leader Volker Kauder

FREE now and never miss the top politics stories again. SUBSCRIBE Invalid email Sign up fornow and never miss the top politics stories again. We will use your email address only for sending you newsletters. Please see our Privacy Notice for details of your data protection rights.

The security expert of the conservative CDU party in North Rhine-Westphalia called for the review after it was discovered that three of four terror suspects plotting mass carnage in the city of Duesseldorf were all living in refugee camps and had travelled from Syria disguised as refugees. He said it was "naive" to believe statements from members of his own party that no terrorists had inveigled their way into the country disguised as asylum seekers. He said: "Even now we do not know the identity of everyone.

GETTY Migrant and refugee arrivals at German train station

"The security authorities in North Rhine-Westphalia have to organise an immediate security review of all refugees living in the state."

Our investigating authorities must crack down on suspected terrorists Justice minister Heiko Maas

North Rhine-Westphalia has Duesseldorf as its capital and Cologne as its biggest city. Dozens of migrant men robbed and sexually molested hundreds of women on New Year's Eve in Cologne in scenes which forever changed the German perception of refugees. Hans-Georg Maassen, the head of Germany's internal intelligence agency, had previously said that ISIS did not need to smuggle people into the country in the refugee wave because they had "other means" of launching attacks - including radicalising disaffected converts and Muslims already living in Germany.

GETTY Muslim families try to embrace Germany

But the Duesseldorf cell arrests have changed all that. Justice minister Heiko Maas said: "Our investigating authorities must crack down on suspected terrorists with all means available to them under the law." While intelligence officials speak of the number of suspected fighters smuggling themselves into Germany is "very low," they nevertheless now acknowledge that it has become a strategy of the terror group which occupies large swathes of Iraq and Syria.

Life inside Serbia's migrant camps as borders to Europe remain closed Wed, April 6, 2016 Life inside Serbia's migrant camps as borders to Europe remain closed Play slideshow Adrian Callaghan/Daily Express 1 of 54 I child makes the sign of peace inside a refugee camp, Serbia

GETTY Targets for radicalisation