Danish police said Wednesday they had arrested 20 people suspected of planning "Islamist attacks".
The suspects had tried to acquire weapons and explosive devices, police said. "Police searched 20 addresses and arrested 20 people", Copenhagen police chief Jorgen Bergen Skov said at a press conference.
He did not specify the target of the possible attack but said police had arrested all the suspects it had on its radar.
"They are people who have both the intent and ability to commit a terrorist attack," Bergen Skov said.
The suspects will be brought before a judge on Thursday for closed-door hearings. Denmark was last hit by militant attacks in 2015 when Copenhagen's Great Synagogue was targeted in a shooting which saw one security officer killed after an earlier attack on a conference on freedom of expression also left one person dead.
Five police officers were injured in the twin attacks. Officers gunned down and killed the 22-year-old perpetrator Omar El-Hussein, a Danish citizen of Palestinian origin who had pledged allegiance to the Islamic State (IS) group.