By Vegard Botterli

OSLO (Reuters) - A Rwandan man pleaded not guilty to organizing the murder of 2,000 people in the 1994 genocide in the African country as his trial opened in a Norwegian court on Tuesday.

Sadi Bugingo, 47, a former businessman, is accused of taking a leading role in planning and leading attacks against Tutsi civilians who sought refuge in a Catholic centre and a hospital, prosecutors said.

"Bugingo encouraged people in his militia to murder and strengthened people's resolve to kill," prosecutor Petter Mandt told the court hearing the first genocide trial in Norway's history.

More than 800,000 people were killed when Rwanda's Hutu-led government and ethnic militias went on a 100-day killing spree in April 1994, indiscriminately killing Tutsis and moderate Hutus after long-standing ethnic tensions flared up.

Bugingo has lived in Norway since 2002 and was tracked down there by Rwandan prosecutors. He pleaded not guilty to the charges but if convicted, faces a maximum 21-year prison sentence.

"If you commit a war crime, crime against humanity or taken part in genocide, you have to be punished no matter where you live," prosecutor Mandt said.

Bugingo is accused to taking part in attacks at the St. Joseph Catholic centre and municipal building in Kibungo and also leading a group that dragged victims from the hospital to kill them at a brick factory. He is not charged with carrying out the murders himself.

Witnesses said Hutu militants surrounded the parish and municipal house, threw hand grenades on the buildings and attacked men, women and children with guns, machetes, clubs and sticks.

Norwegian prosecutors have collected more than a 100 witness statements and several survivors are due to travel to Oslo to testify in a trial that is expected to run until December.

Rwanda was also keen to prosecute Bugingo but did not ask for his extradition after Norway assured the government it would provide all the necessary resources.

"This is a big case for Rwanda because it gives an impression that the long arm of the law will not tolerate any impunity against a genocide fugitive regardless of where the crime was committed," said Jean Bosco Siboyintore, National Prosecutor at the Genocide Fugitive Tracking Unit in Rwanda.

(Additional reporting by Jenny Clover in KIGALI, Rwanda; Writing by Balazs Koranyi; Editing by Angus MacSwan)