The Irish Government made a desperate appeal to the Filipino authorities to call off a planned military operation to free Fr Michael Sinnott fearing the kidnapped priest would be killed in the crossfire.

The Filipino military was seeking authority for an armed rescue attempt as late as Monday, just three days before the Irish missionary was finally freed unharmed.

However, after learning of the plan, Irish Ambassador Richard O'Brien begged officials in the president's office not to give the green light.

It is understood the military was planning on at least two occasions to use force to rescue Fr Sinnott (79) before they were dissuaded by Irish officials.

As the freed missionary, originally from Barntown in Co Wexford, recovers at the Columban Fathers' headquarters in Manila, a full picture of the high-level international efforts to rescue him is beginning to emerge.

The Irish authorities had repeatedly called for a peaceful solution to the hostage crisis and secured the help of US Secretary of State Hillary Clinton, as well as various Middle Eastern states. Mrs Clinton had agreed that she would raise the plight of Fr Sinnott with the Filipino government on her state visit there this week.

However, tensions rose on Monday when news emerged that Islamic extremist group Abu Sayyaf had beheaded a local school principal.

Fr Sinnott was eventually freed at 4.30am local time on Thursday after 32 days in captivity. He was handed over by members of the Moro Islamic Liberation Front (MILF) to government officials.

The missionary, who underwent a quadruple heart bypass operation four years ago, was deprived of his medication for a number of days following his kidnapping in the northern city of Pagadian on October 11.

The Republic's Foreign Affairs Minister Micheal Martin is understood to have used go-betweens from a number of Arab countries to make contact with the commander-in-chief of MILF to urge them to provide the elderly priest with his medication.

Following his release, Fr Sinnott told how his captors ordered him to write a list of the five heart drugs he needed and that these were later given to him.

Fr Pat Raleigh, vice-director of the Columbans in Ireland, said a Mass of thanksgiving will be held at the order's headquarters at Dalgan Park in Navan, Co Meath, on Sunday.

"It's a time for rejoicing, particularly for his family, but also for all Columbans," he added.