Eight young men have been arrested in Denmark in connection with an alleged plot to carry out a bombing.
Jakob Scharf, the director general of the Danish intelligence service PET, said the arrests near the capital Copenhagen on Tuesday had "prevented a terrorist attack".
"We would describe the main suspects as militant Islamists with international contacts, including leading members of al-Qaeda," he said.
Scharf would not disclose any information about the possible target, but said there was "no direct link" to Denmark's involvement in Iraq or Afghanistan.
Police raided 11 homes in the early hours of Tuesday.
Television footage shot from a helicopter showed bomb squads and forensics officers at some of the locations.
'Unstable explosive'
"We made our move now because we had gathered enough evidence to make an arrest, and because several of the suspects had created an unstable explosive in a densely populated housing area," he said.
"During the raids overnight and this morning we found a series of objects and materials that are important in this case," he added.
Six of the eight suspects were Danish citizens and the had foreign backgrounds from Afghanistan, Pakistan, Somalia and Turkey, and six of the eight held Danish citizenship, Scharf said.
"This is a serious case. A case which we have been investigating very intensively... A case which has required much of PET's resources, a case which has had high priority for us," he added.
This is the third time in two years that Danish police have arrested people it suspects of preparing acts of terrorism.
In September 2006, PET arrested nine people after finding chemicals used in explosives production during a raid. Four young Muslims were indicted and accused of planning attacks in Denmark or abroad. Their trial is to begin on Wednesday.
Denmark has not been targeted by a terrorist attack for more than two decades.