Four members of the Islamist militant group Hamas have been detained on suspicion of planning attacks on Jewish institutions in Europe, German prosecutors said in a statement.

The weapons were due to be taken to Berlin and kept at the ready for potential terrorist attacks against Jewish institutions, said prosecutors.

The Danish Security and Intelligence Service PET said in August that the threat towards Denmark had intensified after anti-Islam activists damaged several copies of the Koran over the summer.

“The investigation has revealed that a network of people has been preparing a terrorist act,” Flemming Drejer, PET chief superintendent, told a press briefing in Copenhagen.

“This is extremely serious,” Danish Prime Minister Mette Frederiksen told news agency Ritzau at a meeting with EU leaders in Brussels.

The three arrested in Denmark would be charged under the terrorism clause of the criminal code and put in front of a judge for preliminary questioning, police said.

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