A Burundian rebel has admitted being involved in an ambush that killed the Vatican's ambassador to the country in December, according to the army.
The Vatican was dismay at the monsignor's death
The captured 20-year-old told the army that rebels had been ordered to fire on cars that did not stop and did not target Monsignor Michael Courtney.
The National Liberation Forces (FNL) angrily denied responsibility for the death at the time.
The army and FNL have been locked in intense fighting over the past week.
Michael Courtney, 58, from Ireland, was shot three times in an FNL stronghold.
He had played a key role in persuading other rebel groups to join the peace process and had been urging the FNL to follow suit.
He had served as ambassador to Burundi since 2000.
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.