The Irish Ambassador to Singapore has travelled to Manila to support the efforts to release kidnapped priest Fr Michael Sinnott.
Philippine security forces combed coastal areas on the southern island of Mindanao to locate gunmen holding the priest, who is originally from Wexford.
Church leaders appealed to the kidnappers to free the ailing man.
An extensive police and military search is under way following the abduction of the Columban Father.
He was abducted by an armed gang in the city of Pagadian while taking a stroll yesterday evening.
Witnesses have said the priest was bundled into a van and later dragged to a boat.
Ambassador Richard O'Brien who is accredited to the Philippines is expected to discuss the kidnapping with foreign ministry officials and police.
He will also meet representatives of the Columban Father in Manila.
No group has claimed responsibility for the abduction, however, police and military said they suspect that either the al Qaeda-linked Abu Sayyaf group or the Moro Islamic Liberation Front were involved.
Fr Sinnott was forcibly dragged away at gunpoint and transferred to a waiting van, which was subsequently found abandoned near a coastal area.
One witness said he was then beaten up and transferred to a small motorised boat.
The 79-year-old priest underwent heart by-pass surgery a few years ago.
Pagadian Archbishop Emmanuel Cabajar has appealed to Fr Sinnott's captors to free the priest.
'I am concerned about his safety. I am calling on his captors to free him. Please do not hurt him,' Archbishop Cabajar said.
Speaking on RTÉ's Morning Ireland, a fellow Columban priest said Fr Sinnott does not have his medication with him.
Fr Dan O'Malley said Fr Sinnott's family are still coming to terms with news of the kidnap.
President Mary McAleese has expressed her concern for the safety of Fr Sinnott.
‘This is a most difficult time for Fr Michael's family and the entire Columban Community. Lets hope that those who seized him will reflect on what they have done and realease this elderly, hard-working priest back to his community and to his work,’ she said.
Fr Sinnott is the third Irish priest from the Columban Society to be kidnapped in the area since 1997.
The area is home to several Muslim radical groups, including the Abu Sayyaf, notorious for high-profile kidnappings. The Abu Sayyaf kidnapped Italian priest Giancarlo Bossi in 2007 and later released him.
In January, Muslim rebels kidnapped three Red Cross workers, including an Italian and Swiss national, on a remote southern island, but set them free after several months.
