Police detained five more suspects Thursday in the deaths of three men who were found with their throats slit in a publishing house that prints Bibles, the latest in a string of attacks targeting Christians in the mostly Muslim country.

The arrests brought to 10 the number of suspects in custody, all people in their late teens or early 20s, said Halil Ibrahim Dasoz, governor of Malatya, the city in central Turkey where the killings took place.

Malatya is known as hotbed of Turkish nationalism and as the hometown of Mehmet Ali Agca, the gunman who tried to assassinate Pope John Paul II in 1981.

Local media said five suspects detained Wednesday were college students who were living at a residence that belongs to an Islamic foundation. Some of those suspects told investigators they carried out the killings to protect Islam, a Turkish newspaper reported.

"We didn't do this for ourselves, but for our religion," Hurriyet newspaper quoted one suspect as saying. "Our religion is being destroyed. Let this be a lesson to enemies of our religion."

Turkey, a predominantly Muslim country bidding for EU membership, has been criticized for not doing enough to protect its religious minorities and to check rising Turkish nationalism and hostility toward non-Muslims.

The three victims — a German and two Turkish citizens — were found with their hands and legs bound and their throats slit at the Zirve publishing house.

All were employees of the publishing house, which printed Bibles and Christian literature, had been targeted previously in protests by nationalists who accused it of proselytizing in this officially secular country.

The German man had been living in Malatya since 2003, the mayor said. Anatolia identified him as 46-year-old Tilman Ekkehart Geske.

"Nothing can excuse such an attack that comes at a time of great need for peace, brotherhood and tolerance," President Ahmet Necdet Sezer said.

Prime Minister Recep Tayyip Erdogan described the attack as "savagery."

The five suspects detained Wednesday had each had been carrying copies of a letter that read: "We five are brothers. We are going to our deaths. We may not return," according to the state-run Anatolia news agency.

Police said one suspect underwent surgery for head injuries after he apparently tried to escape by jumping from a window.

Making up less than 1 percent of Turkey's 70 million people, Christians have increasingly become targets amid what some fear is a rising tide of hostility toward non-Muslims.

In February 2006, a teenager fatally shot a Catholic priest as he prayed in his church, and two more Catholic priests were attacked later in the year. A November visit by Pope Benedict XVI was greeted by nonviolent protests, and early this year a gunman killed Armenian Christian editor Hrant Dink.

Authorities had vowed to deal with extremist attacks after Dink's murder, but Wednesday's assault showed the violence was not slowing down.

"The killing is a result of provocations in Turkey against minorities," said Orhan Kemal Cengiz, a lawyer for one of the victims, Necati Aydin. "Intolerance in general has been rising sharply in Turkey."

The attack came ahead of presidential elections next month, a contest that highlights fears among Turkey's secular establishment that a candidate from Erdogan's Islamic-rooted party, or even Erdogan himself, could win the job and strengthen Islamic influence on the government.

Last weekend, hundreds of thousands of pro-secular protesters demonstrated in the capital, Ankara. Erdogan has rejected the label of "Islamist," citing his commitment to the EU bid.

The Vatican's envoy to Turkey, Mons. Antonio Lucibello, told Italian daily Il Messaggero that he thought the attack was a "sporadic event."

"We are not afraid. I'm not afraid," he said.

German Foreign Minister Frank-Walter Steinmeier condemned the attack "in the strongest terms," and said he expected Turkish authorities would "do everything to clear up this crime completely and bring those responsible to justice."

German Chancellor Angela Merkel's Christian Democrat Party — which opposes Turkey's bid to join the EU — said the attacks showed the country's shortcomings in protecting religious freedoms.

A group of 150 lit candles and unfolded a banner that read "We are all Christians" in downtown Istanbul but the numbers were far less than with Dink's murder, which was followed by widespread protests and condemnations. More than 100,000 people marched at Dink's funeral.