Philippine security forces on Saturday killed a foreign national and his female companion who were suspected of being connected to a militant group supporting Islamic State, police officials said, two days after the group's leader was also killed. The foreigner, believed to be Pakistani and identified as Abu Naila, resisted arrest and attempted to throw a grenade while a police and military team was conducting a manhunt in Sarangani province, Chief Superintendent Cedrick Train, a police regional director, said. They were conducting an operation against members of the militant Ansar Al-Khilafah Philippines (AKP), one of a handful of small groups that have pledged allegiance to Islamic State and blamed for years of unrest in the Philippine south. On Thursday, police chief Ronald dela Rosa said security forces had effectively broken the backbone of AKP with the killing of its leader, Mohammad Jaafar Maguid, and the arrest of his three AKP colleagues. He has warned of "retaliation" by other AKP members and said security forces were on full alert as Filipino Catholics are set to celebrate the feast of the Black Nazarene, with millions of devotees expected to join processions on Monday in several parts of the country, including Manila. Authorities have linked Maguid's group to several crimes ranging from arson and murder to bombings. Regional police spokesman Romeo Galgo said they were still verifying the nationality of the foreigner killed on Saturday. "Officers were forced to fire at the suspects when the grenade was lobbed at them," Train said. President Rodrigo Duterte has warned against Islamic State taking root in the southeast Asian country, saying it needed to avoid "contamination".