Five people have been arrested on suspicion of planning an attack on a Danish newspaper that published controversial caricatures of the Muslim prophet Mohammed in 2005, the Danish secret service PET said Wednesday.
Police said they had seized a submachine gun with a silencer as well as plastic cable bands for tying people up, dpa reported.
Police believed the plotters planned to storm the newspaper offices and "kill as many as possible," PET head Jakob Scharf later told reporters.
Prime Minister Lars Lokke Rasmussen said he was shocked by the plot, saying it showed Denmark faced a serious terror threat. But the country would not change its "open society" values and would protect freedom of speech, he said.
Justice Minister Lars Barfoed described the plot as "the most serious to date in Denmark," in an email to Danish news agency Ritzau.
The PET said that an armed "attack against the Copenhagen offices of the Jyllands-Posten" had been imminent.
Four suspects were arrested in Denmark and a further suspect in Sweden.
The five, four of whom lived in Sweden and three of whom had Swedish citizenship, were aged 26 to 44. Two were Tunisian-born, one Lebanese-born, one Iraqi-born and one was a Swedish national whose descent was unknown, the PET statement said.
The suspects were described as militant Islamists and had international ties.
Scharf said the arrests were the result of close cooperation with the Swedish security service.
"A serious terrorist attack in Denmark has been averted thanks to effective and close cooperation," Swedish security service head Anders Danielsson said.
Swedish authorities were prepared to assist the Danish secret service, and had launched a separate enquiry into the suspects with ties to Sweden.
The suspects have not been linked to a suicide attack on December 11 in Stockholm in which a 28-year-old man was the only fatality.
However, authorities would not rule out links between the new arrests and David Headly, a US citizen arrested in that country for his own alleged plans to attack the Danish newspaper.
Headly has allegedly also told police in the United States that he was involved in planning for the November 2008 terrorist attacks in Mumbai and had helped train people in Sweden for attacks in Britain.
The Islamic Council of Denmark (MFR) condemned the plot, saying they rejected all acts of terror.
The Jyllands-Posten has been the target of several alleged plots since the publication of the caricatures. Almost exactly a year ago, an axe-wielding man forced his way into cartoonist Kurt Westergaard's home.
Westergaard had made a cartoon of the prophet Mohammed with a bomb in his turban.
In September, a Chechen-born man was arrested in Copenhagen after a blast in a hotel toilet. Police said they suspected the man had been planning to target the Jyllands-Posten newspaper.
Scharf said the terror alert level was not affected by the arrests. The Swedish secret service made a similar assessment.
