A letter from the suspected Muslim killer of a Dutch filmmaker pinned to his body held death threats from an unknown terrorist "movement" against a politician, the screenwriter of a movie criticizing Islam, the justice minister said Thursday. Authorities were investigating possible links between the case and foreign terror groups.

Dutch authorities have arrested nine suspects, all believed to be Islamic radicals, in connection with Tuesday's shooting and stabbing of Theo van Gogh (search).

Justice Minister Piet Hein Donner said Thursday the note, stuck to the body with a knife, contained a "direct warning" to the screenwriter, Ayaan Hirsi Ali (search), a Somali-born member of parliament who has outraged fellow Muslims by criticizing Islamic customs and the failure of Muslim families to adopt Dutch ways. She had been under police protection before the slaying.

Donner said the way the five-page letter "was presented indicates that it is not from one person, but a movement." It was neatly typed and written in Dutch and Arabic. A testament found in the suspect's pocket was titled "Drenched in blood" and "these are my last words."

The letter is titled "Open Letter to Hirsi Ali" and threatens a holy war against infidels, America, Europe, the Netherlands and Hirsi Ali. "Saifu Deen alMuwahhied," or "the unifying sword of religion" is written at the bottom of the last page, apparently as a signature.

"It is worrying because it gives the impression it is not the message of an individual, but a wider organization," Donner said. Security has been increased for individuals considered possible targets, including Hirsi Ali and members of her party, he said.

The letter read that Islam would "be victorious through the blood of martyrs." It contained apparent quotes from the Quran, and verses of poetry. "Only the death will separate the truth from the lies," it said.

Somali-born Ayaan Hirsi Ali, who calls herself an ex-Muslim, renounced the Muslim faith of her birth. Van Gogh, the great-grandson of painter Vincent Van Gogh's (search) brother, released the fictional film "Submission" in August. In the film, a veiled Muslim woman spoke about her violent marriage, being raped by a relative and later brutally punished for adultery. In some scenes, the actress' naked body is shown through a transparent gown. One scene shows her body with Quranic verses on it.

The chief suspect in the Van Gogh's killing, who has been identified only as Mohammed B., 26, holds dual Dutch-Moroccan nationality. He was arrested after being wounded in the leg during a shootout with police shortly after the slaying and was to appear before a judge Friday, when prosecutors said they would file charges.

It was not clear what charges the other eight suspects, all of North African descent, would face.

Mohammed B.'s lawyer, Jan Peter Plasman, protested the release of the letter, saying it would prejudice the case against his client. He declined to comment on whether his client was innocent.

A Moroccan diplomat has traveled to the Netherlands to assist in the investigation, and more than 75 detectives have been put on the case, Dutch officials said.

Authorities described Mohammed B. as "an associate" of five men who were briefly detained last year, prosecutors said.

The five had been suspected of providing support to terrorists in Spain and Morocco who were responsible for the bombing in Casablanca in May 2003, Donner told parliament at the time.

But there had been insufficient evidence to prove any charges, and the five were released.

Four of them were among those arrested this week. The fifth was Samir Azzouz, an 18-year-old of Moroccan descent who was arrested in June and is awaiting trial for allegedly planning to attack a Dutch airport, nuclear reactor or Parliament.

Since the Sept. 11, 2001, attacks in the United States, the Dutch secret service has repeatedly warned that the Netherlands could be a target. It is shadowing 150 extremists around the clock and has said that Muslim immigrant youths are being recruited.

The Dutch public has widely perceived Van Gogh's killing as an attack on free speech. Politicians have called for an emergency debate on security officials' failure to prevent it.

Despite widespread condemnation of the murder by mainstream Muslim groups, Muslims fear reprisals, and ethnic tension was evident in Dutch streets.

"This is definitely going to happen more often," said Nicolette Toering, visiting the spot where Van Gogh was killed. She rejected Muslims' concerns of being targeted by violence and said unemployed immigrants should leave the country.

Samir Alami, a Dutch-born man of Moroccan descent, said he felt uncomfortable in the Netherlands for the first time while riding the train to Amsterdam to visit the crime scene. "People were giving me angry stares, you could see it in their faces," he said. "I feel terrible."

Van Gogh will be cremated on Tuesday in a public service.