The torture and killing of three Christians in Turkey in 2007 has seen five men sentenced to prison after being found guilty of premeditated murder.

Tilmann Geske, a 45-year-old German missionary, Uğur Yüksel, 32, and Necati Aydın, 36 – the latter both Turks who had converted from Islam to Christianity – were bound together, tortured and then had their throats slit in the office of the Zirve Publishing House in Malatya, southeastern Turkey, on Easter Sunday in 2007.

The defendants were found and arrested at the publishing house – which printed Bibles – immediately after the crime. A number of other people were arrested later in connection with the incident.

In total, 21 defendants stood trial on Wednesday in the 115th hearing of the case. The five men found guilty of premeditated murder – Emre Günaydın, Cuma Özdemir, Hamit Çeker, Salih Gürler and Abuzer Yıldırım – received three consecutive life sentences each.

Two military officers were sentenced to 14 years in prison for "violating secret communications and forging official documents" and 16 people were acquitted.

According to Christianity Today, some local Christians say Gunaydin pretended to be interested in Christianity in order to get close to the three men killed.

Rev Ihsan Ozbek of the Association of Protestant Churches in Turkey said Gunaydin's last words in court on Wednesday showed no sign of remorse. "I am thankful that I did not shame my country or cause any embarrassment," Gunaydin said.

Though the perpetrators were yesterday found guilty, they were allowed to walk free from court because they have already served five years in detention – the legal limit for detention pending trial in Turkey – and their case now moves to the Court of Appeals.

This has caused outrage among campaigners, as the suspects were already released from prison in March 2007 on condition they wore electronic bracelets.

"Of course the legal process will continue as the case proceeds to the regional administrative court, and then will go to the Supreme Court. This process can take years, and the killers of our brothers brutally murdered can move around freely for years to come. The repeated postponement of the punishment they deserve severely wounds confidence in justice," Ozbek said in a statement.

"As the Protestant community we want the procedure for the case to be performed quickly in order that the trial will be brought to a just conclusion with the punishment of the perpetrators. We hope that the dark powers... will be brought to light soon."

Turkey has a strong Christian heritage – the apostle Paul and Timothy were both born there, and the city of Antioch, now Antakya, was known as "the cradle of Christianity" – but a series of genocides in the early 20th century killed much of the Christian population. The collapse of the Ottoman Empire in 1923 also forced many Armenians, Assyrians, Greeks and Georgians to leave the country, and the population of Turkey is now more than 97 per cent Muslim.