The Vatican expressed dismay at the monsignor's death

Papal nuncio Michael Courtney, 58, an Irish national, was killed as he was travelling by car in the south of the country, the Vatican confirmed.

Burundi's president, who rushed to the hospital where the nuncio was taken, said it was a deliberate attack.

But the rebels have denied any involvement and in turn accused the military of being responsible.

The Vatican has expressed "deep sorrow" at the diplomat's death, describing him as "a faithful and generous servant of the Church."

Monsignor Courtney, who was shot three times, died during emergency surgery in the capital's Prince Louis Rwagasaore hospital at around 1800 local time (1400 GMT).

"We were trying everything we could to save him. We were trying to extract the bullets and he died while we were operating," an employee at the hospital told AFP news agency.

President Domitien Ndayizeye, speaking from the hospital, said: "It was an ambush. They shot to kill him."

Those who killed Monsignor Courtney would be brought to justice, the president vowed, noting that the area where he was killed was a stronghold of rebels from the National Liberation Forces (FNL).

Rebels blamed

Chief of army staff General Germain Niyoyankana told AFP that FNL rebels were behind the attack.

But the FNL, which remains outside the peace process, denied the accusation.

"We knew where he lived... We could have killed him if we wished. We strongly condemn those who killed him," rebel spokesman Pasteur Habimana said.

The Missionary Service News Agency (Misna) in Rome said that Monsignor Courtney had been travelling by car with three other people when their vehicle was sprayed with gunfire in Minago, Bururi province.

The other occupants escaped unharmed or with light injuries.

Mariano Benni of Misna told CNN that several sources had said the killing was an accident.

Monsignor Courtney had served as ambassador to Burundi since 2000.

Father Claudio Marano, a missionary in Burundi, told Vatican Radio that he had met all the various groups several times and the entire government.

"He was working a lot in favour of peace and reconciliation in Burundi," Father Marano said.

Some 300,000 people have been killed in Burundi's decade-old civil war, in which rebels of the majority Hutu group are fighting to end dominance of the Tutsi minority.

The largest rebel group, the Forces for the Defence of Democracy, has recently joined the government and its fighters are being integrated into the army but the FNL refuses to negotiate with the government.