The Philippines government has said the resumption of peace talks with insurgents could be jeopardised after the rebels were accused of involvement in the abduction of Fr Michael Sinnott.
The armed forces and the police have both received intelligence reports that rogue elements of the Moro Islamic Liberation Front (MILF) were behind the 11 October kidnapping of Fr Sinnott.
While the government 'would like to give them the benefit of the doubt,' the MILF leadership must impose 'punishment or sanction against those involved to show good faith and that they are very sincere,' presidential spokeswoman Lorelei Fajardo told reporters.
Separately, Interior Secretary Ronaldo Puno said the police had intelligence reports that an MILF unit was behind the abduction.
'It is clear to us that the kidnappers are either directly connected to or very closely associated to the MILF,' Mr Puno said, identifying a 'Commander Al Asree' as the ringleader.
Ms Fajardo said it was possible that the MILF leadership was not aware that some of its members were involved, noting earlier denials from the group.
'We hope that this is an isolated case, so we have to be very careful in handling this,' Ms Fajardo said.
Asked whether the incident could affect the peace talks, she said: 'There might be some respite in peace talks, but we have to continue (the talks at some stage).'
The 79-year-old priest, who has a history of heart problems, was kidnapped by six armed men from the compound of the Society of St Columban mission house in Pagadian city on the strife-torn southern island of Mindanao.
He was believed to have been taken to a jungle area in nearby Lanao del Norte province where MILF rebels and other armed groups operate.
Yesterday, the military said a video of Fr Sinnott released by the kidnappers at the weekend in which the priest relayed a $2m ransom demand, had given them clues about the identity of his captors and the location where he was being kept.
The Philippines government as well as the Columban order have rejected the ransom demand.
Peace talks with the MILF have been stalled since last year, when two MILF commanders broke a five-year-old ceasefire and launched large-scale attacks across Mindanao.
