Police have detained five more suspects 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 occurred.

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 and 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 Tilman Ekkehart Geske, 46.

"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."

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