A United Nations war crimes court for Rwanda sentenced a Roman Catholic priest to life in prison for his role in Rwanda's 1994 genocide that left 800,000 dead.

The Rev. Athanase Seromba was the first Catholic priest charged with genocide by the International Criminal Court for Rwanda and his jail sentence was increased on Wednesday from 15 years to life.

"He committed genocide as well as extermination as a crime against humanity by virtue of his role in the destruction of the church," said Judge Mohamed Shahabuddeen. "The acts of Seromba are sufficient to constitute direct participation in the crimes."

In April 1994, some 1,500 refugees flocked to Seromba's church in the town of Nyange to take shelter as then-government soldiers and Hutu extremists rounded up ethnic Tutsi and moderate Hutu for slaughter across Rwanda.

Prosecutors say Seromba, an ethnic Hutu, had the church destroyed by bulldozers and ordered gunmen to shoot any Tutsis who tried to flee or survived the carnage.

In 2002, Seromba turned himself in after fleeing Rwanda.

Seromba was one of five clergymen - all of whom are Rwandan citizens - who were accused of taking part in the Rwandan genocide. Prosecutors maintained that the five collaborated with killers in their congregations during the 1994 civil war.

There are many reports of pastors, priests and church workers who helped save people during the massacres. But there is also evidence that thousands of refugees seeking shelter in churches, missions and parishes were trapped and killed.

Christians make up the majority of the Rwandan population and the largest single denomination is Roman Catholic. Three of the five accused clergymen are Roman Catholic priests.

Seromba has denied the charges and has claimed innocence. In a 2006 U.N. court ruling, he was convicted and sentenced 15 years imprisonment.

Prosecutors claimed the sentence was too light and this week, the court found favour of the prosecution, increasing his sentence, as reported by Agence France-Press.