Police officials however have said they suspect the gunmen came either from the al-Qaeda-linked Abu Sayyaf group, or from the Moro Islamic Liberation Front, both of which are active in the area.
"We've alerted all our units as well as the military to be on the lookout and intercept the gunmen," Angelo Sunglao, police chief in western Mindanao region, told reporters.
Sinnott's group, the Missionary Society of St Columban, said the priest was taking a Sunday evening stroll in the convent's garden when he was taken.
They appealed for prayers for his safe recovery.
One church official said he was particularly concerned for Sinnott's well-being, because he has a heart condition and was not carrying his medication when he was taken.