A Cambodian court Tuesday found four former Khmer Rouge guerillas guilty of the 1996 kidnapping and murder of a British deminer and his Cambodian translator and sentenced them to 10 to 20 years in prison.

Judge Iv Kim Sri of the Phnom Penh Municipal Court acquitted a fifth man because of a lack of evidence.

Briton Christopher Howes, his translator Huon Hourth and about 30 other people were abducted by Khmer Rouge guerillas near Siem Reap, about 300 kilometres from Phnom Penh and home to Angkor Wat, an ancient temple complex and World Heritage Site.

During an October 4 hearing, the court heard that Howes, 37, had acted heroically, negotiating the release of all but himself and Hourth before the pair were marched to the rebel stronghold of Anlong Veng, 125 kilometres north of Siem Reap and home to Khmer Rouge military commander Ta Mok and the movement's leader Pol Pot, both of whom have since died without facing trial.

Howes and Hourth were shot at close range and cremated, the court heard.

Khem Nguon, 59; Loch Mao, 54; and Puth Lim were each sentenced to 20 years in prison. Sin Dorn, 52, was ordered to serve 10 years, and Cheath Chet, 34, was released.

Nguon and Lim were also ordered to pay 10,000 dollars in compensation to the victims' families.

The convicted men did not deny involvement but said they were only following orders given by Ta Mok and Pol Pot. Iv Kim Sri said their claim did not absolve them.

It was not clear if the men would appeal.

"It's not fair," Lim said as he was led from court. "I only burned the body."

The man branded the ringleader by his co-defendants, Nguon, covered his face as the verdict was read and he was led away.

Rupert Leighton - country programme manager of the Manchester-based Mines Advisory Group, which Howes worked for - said outside the court that the basic principle that humanitarian workers were immune to attack had been upheld by the court.

The demining centre, which is still active in Cambodia, released a statement from Howes' family members after the verdict was read.

"My father, Roy Howes, and I welcome the verdict of the court and feel that at last justice has been done," Howes' sister Patricia Phillips wrote. "Although we have never sought revenge, we are pleased that the murderers ... have been brought to account."

Howes' mother died in 2007.

The Khmer Rouge ruled Cambodia from 1975 to 1979, when it attempted to transform it into an agrarian society, resulting in the emptying of Cambodia's cities, forced labour, executions and starvation. About a fifth of the country's population, or up to 2 million people, died.

By 1996, the Khmer Rouge had become a band of guerillas based in the remote north and north-west of the country with orders to kill foreigners, and although ransom demands were not uncommon as the rebels attempted to fund their resistance, few people were released.