ODENSE, Denmark — Police raided homes in a largely immigrant suburb before dawn yesterday, detaining nine men for allegedly preparing explosives for a terror attack in Denmark, which drew outcries from Muslims earlier this year over caricatures of Islam’s founder.

Seven men were later arraigned on preliminary charges of plotting a terror attack, but the other two were released. An Islamic imam, Abu Bashar, said the suspects were Muslims.

Officials in Odense, the country’s third-biggest city, did not disclose the planned target and said it was hard to evaluate how far the alleged plot had progressed.

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

The raids, days ahead of the anniversary of the September 11, 2001, attacks, came after two recent sweeps by British police, one that allegedly thwarted a plot to bomb jetliners over the Atlantic and another that arrested a group purportedly trying to recruit and train people for terror attacks. Germany also arrested four people in botched train bombings.

News of the arrests sent jitters through Denmark, which heightened its terror preparedness early this year following protests from Muslims around the world over caricatures of the Prophet Muhammad that were first published in a Danish newspaper.

Justice Minister Lene Espersen said she did not know whether the plot was related to the cartoon crisis in February, when Danish and other Western embassies were attacked by mobs in Islamic countries.

Ms. Espersen called the case “the most serious matter” during her time as justice minister. “The clues police found indicate that they were very likely planning an attack somewhere in Denmark,” she told the Associated Press.

Identities of the arrested men were not released, but authorities said all were Danish citizens aged 18–33 and that all but one had immigrant backgrounds. They were arrested in Vollsmose, an Odense suburb where many residents are immigrants.

The seven suspects facing charges arrived for a closed court hearing in Odense, handcuffed with plastic strips that were removed upon the request of the defense lawyers.

Prosecutor Erik Terp Jensen urged they be kept in custody on preliminary charges of plotting terror acts as the investigation continues. The maximum sentence is life in prison, although such sentences are commuted after 16 years under Danish law.

Witnesses said several more people had been rounded up in the raids but were released after police checked their identities.

Mahir Arrar, 18, said he was with a friend at Odense’s harbor when police took them both to a police station. Mr. Arrar said he was released but that his friend, whom he declined to identify, remained in custody.

“I believe this is a big misunderstanding,” Mr. Arrar said outside the courthouse.

Another man, who identified himself only as Ali K., said police detained his whole family but released everyone except his 21-year-old brother. “They looked for weapons, but they have found nothing. They also searched our basement,” he told AP.

Authorities said the suspect group had been under surveillance for some time. But Mr. Findsen said the sweep was not related to neighboring Germany’s arrest of four Lebanese suspected of involvement in a failed attempt to bomb trains.

German journalists have said one of those suspects, Youssef Mohamad el Hajdib, was heading to Denmark, and German and Danish press outlets said German police found a telephone number in his pocket for Abu Bashar, the imam in Odense who identified the suspects arrested yesterday as Muslims.

Abu Bashar denied knowing Mr. Hajdib but said it is a just matter of time before terrorists strike in Denmark.

“Osama bin Laden said in a message three years ago that he will punish the countries that have [troops] in Iraq,” Abu Bashar told AP.” Denmark is on the list.”

About 500 Danish soldiers are serving in southern Iraq under British command, and 360 more are in Afghanistan as part of the NATO-led force.

Terrorists have not hit Denmark since 1985, when a bomb exploded outside the offices of North West Orient Airlines in Copenhagen, killing one person and wounding 16. Three Palestinian Arabs living in Sweden were convicted and sentenced to life in prison in 1989.