Danish authorities said they foiled a serious terror plot when nine men accused of preparing explosives for a planned attack in Denmark were arrested in pre-dawn raids Tuesday.

Investigators were not sure what stages the plans were in, but decided to launch a pre-emptive strike after keeping the group under surveillance for some time.

"The clues police found indicate that they were very likely planning an attack somewhere in Denmark," Justice Minister Lene Espersen told The Associated Press.

"It was the most serious matter I have had in my time as justice minister," she said. "Police went in and stopped the group as it was preparing an attack."

Anti-terror squads carried out the sweep at 2 a.m. (0000GMT) in Vollsmose, a mostly immigrant suburb of Odense.

Lars Findsen, the head of the Danish Security Intelligence Service, said the suspects "had acquired material ... to build explosives in connection with the preparation of a terror act."

CountryWatch: Denmark

Denmark raised its terror preparedness level after attacks in recent years in London and Madrid and the global Muslim fury earlier this year over caricatures of the Prophet Muhammad first published in a Danish newspaper.

Espersen said she did not know whether the case was related to the cartoon crisis in February, when Danish and other Western embassies were set ablaze by angry crowds in Muslim countries.

Tuesday's arrests would not prompt the Scandinavian country to raise its terror alert further, the intelligence service said.

Officials said the suspects were Danish citizens between the ages of 18 and 33. Findsen said eight of them had immigrant backgrounds, but did not specify from what countries.

He did not reveal the planned target of the attack, and said it was hard to evaluate how far the suspects had progressed in their preparations.

"With the general terror situation, the Danish Security Intelligence Service didn't want to run any unnecessary risk," Findsen said.

He said the sweep was not related to a terror investigation in Germany in which four Lebanese suspects are being held in connection with a failed train bombing attempt.

German media claimed one of the suspects, Youssef Mohamad el Hajdib, who was arrested Aug. 19 in the northern German city of Kiel, was heading to Denmark. German and Danish media reported that German police had found a telephone number in his pocket for Abu Bashar, an imam living in Odense.

Abu Bashar denied knowing el Hajdib, but said it was a matter of time before terrorists would strike Denmark.

"Usama Bin Laden said in a message three years ago that he will punish the countries that have (troops) in Iraq," he told the AP. "Denmark is on the list. I am afraid of the message of Usama Bin Laden that he will do something against Denmark."

Denmark has about 500 troops in southern Iraq under British command and 360 more in Afghanistan as part of the NATO-led force.

Abu Bashar said he knew the suspects arrested Tuesday as members of Odense's Muslim community, and predicted they would be found innocent.

"I believe that very, very soon they will be released," he said.

Two weeks ago, four suspects in custody in Denmark since October were charged with supplying explosives to two men arrested in Bosnia for allegedly preparing a terror attack.

Investigators said that group planned to blow up a target in a European country to force the withdrawal of foreign troops from Afghanistan and Iraq.

Police did not say whether the new arrests were related to that case.

Terrorists have not hit Denmark in 20 years, but the July 2005 bombings in London stirred fears that the Scandinavian country could be targeted for its participation in the U.S.-led coalition in Iraq.

"We have seen the faces of terror in Madrid and London. We know that there are potential terror threats in the whole Western world," Denmark's Deputy Prime Minister Bendt Bendtsen told DR public television.

In 1985, a bomb exploded outside the offices of North West Orient airlines in Copenhagen, killing one person and wounding 16. Three Palestinians living in Sweden were convicted of planting the bombs and sentenced to life in prison in 1989.