Istanbul, Turkey ? Assailants on Wednesday slit the throats of three employees of a publishing house that distributes Bibles, the latest in a series of attacks targeting Turkey’s small Christian minority.

The attack added to concerns in Europe about whether the predominantly Muslim country – which is bidding for EU membership – can protect its religious minorities. It also underlined concerns about rising Turkish nationalism and hostility toward non-Muslims.

The three victims – a German and two Turks – were found with their hands and legs bound and their throats slit at the Zirve publishing house in the central city of Malatya.

Police detained four men, ages 19 to 20, and a fifth suspect was hospitalized with serious injuries after jumping out of a window to try to escape arrest, authorities said. All five were carrying a letter that read: “We five are brothers. We are going to our deaths,” according to the state-run Anatolia news agency.

Prime Minister Recep Tayyip Erdogan condemned the attack and said investigators were looking into whether there were other suspects or possible links with terror groups.

“This is savagery,” Erdogan said.

The German victim had been living in Malatya since 2003, said Gov. Halil Ibrahim Dasoz. Anatolia identified him as 46-year-old Tilman Ekkehart Geske.

The attack is the latest in a string of attacks on Turkey’s Christian community, which comprises less than 1 percent of the population. In February 2006, a Turkish teenager shot a Roman Catholic priest to death as he prayed in his church, and two other priests were attacked later that year. A November visit by Pope Benedict XVI was greeted by several nonviolent protests. Earlier this year, a suspected nationalist killed Armenian Christian editor Hrant Dink.

Authorities had vowed to deal with extremists after Dink’s murder, but Wednesday’s attack showed the violence was not slowing down.

German Chancellor Angela Merkel’s Christian Democrat Party – which opposes Muslim Turkey’s membership in the European Union – said the attacks showed the country’s shortcomings in protecting religious freedom.

“After today’s murders, the Turkish government must … be asked whether it is doing enough to protect religious minorities,” the party’s general secretary, Ronald Pofalla, said in a statement.

“Freedom of religion is one of the fundamental human rights. The Turkish state is still far from the freedom of religion that marks Europe. It is the task of the Turkish government to guarantee this freedom of religion,” the statement said.

About 150 people lit candles and unfolded a banner that read, “We are all Christians,” in downtown Istanbul to protest the attack and show solidarity with the Christian community. But there was far less public outcry than with Dink’s murder, which was followed by widespread protests and condemnations. More than 100,000 people marched at Dink’s funeral.

Malatya, known as a hotbed of nationalists, is the hometown of Mehmet Ali Agca, who shot Pope John Paul II in 1981.