Police secure the area in front of an embassy in Copenhagen on January 27, 2023. (PHOTO / AFP)

COPENHAGEN - Copenhagen police and the Danish Security and Intelligence Service (PET) said on Thursday they had made several arrests in a coordinated action across the country on suspicion of preparation for a terrorist attack.

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

The Danish Security and Intelligence Service has for more than a decade warned against potential attacks, and since 2010 has kept its terrorist alert level at 4 on a scale from 1-5

"For a number of years now, we have seen that there are people living in Denmark who do not wish us well. Who are against our freedom and who are against Danish society, with all that it entails," Frederiksen said.

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She did not elaborate on who the suspected attackers were.

The Copenhagen police and PET called a press briefing at 1200 GMT at the Copenhagen police headquarters.

Police and the intelligence service did not disclose how many arrests were made.

PET has for more than a decade warned against potential attacks, and since 2010 has kept its terrorist alert level at 4 on a scale from 1-5, reflecting a "significant" threat.

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PET acknowledged in August that the threat towards Denmark had intensified after anti-Islam activists damaged several copies of the Koran over the summer, but said at the time there was no reason to increase the alert to the highest level.