The four suspects, aged between 16 and 20, were arrested in and around Copenhagen yesterday and detained in jail as police continued their investigation.
"We had a very short period to investigate but our information indicated that their action was imminent," police spokesman Joern Bro said. He declined to give details, saying only that the network had planned to carry out the suicide attack in Europe.
The arrests were linked to an investigation in Bosnia in which a Turkish, a Swedish and a Bosnian national were arrested in Sarajevo on 19 October on suspicion of preparing a terrorist attack, Bro said.
Police said they found explosives, firearms and other military equipment in connection with those arrests. The Bosnian national has since been released.
Bosnian paper Slobodna Bosna said police also found a video cassette showing three masked men praying and asking God to forgive them for their self-sacrifice.
It said the two suspects being held in Bosnia were a 19-year-old Swede originally from Serbia-Montenegro, and an 18-year-old Turk.
Both arrived in Bosnia about a month ago, according to an anonymous police source quoted by the weekly. They were put under surveillance after Turkey and Sweden tipped off Bosnian authorities, the paper said, adding that police arrested them in a raid weeks later.
Police in Denmark and Bosnia could not confirm the report.
"We don't know exactly what kind of terror (attack) they were planning but our information indicates that it could have been a suicide bomb," Bro said of the arrests in Bosnia, adding that the weapons found could also be used in a "sniper murder."
Bro said the one of the four men arrested in Denmark was a Danish citizen. The nationalities of the other three were not clear but Bro said they were of Middle Eastern origin.
He said the four were in "close contact" with the two men held in Bosnia. One of them - the Turk - lived in Denmark, Bro said.
According to Sarajevo's Dnevni Avaz daily newspaper, one of the three suspects arrested in Bosnia was an 18-year-old preparing a suicide attack on the Sarajevo embassy of a European Union country.
Swedish security police spokesman Jakob Larsson confirmed the Swedish suspect was a resident of the Scandinavian country, but declined to comment further.
The Danish suspects, who were not identified, were ordered detained at a court hearing in Glostrup, a suburb of Copenhagen.
Police said they raided the suspects' homes in Copenhagen and suburbs of the capital, seizing computers, computer discs, books with radical Muslim literature and cellular phones.
About 25 people in all were briefly detained but only the four were arrested.
Danish Prime Minister Anders Fogh Rasmussen said the arrests were "shocking."
Anja Dalgaard-Nielsen, a terrorism expert with the Danish Institute for International Studies, said early information "indicates that these are people that have been inspired by the al-Qaida movement."Reuse content