Suspected Muslim militants have beheaded two kidnapped sawmill workers while four other captives have been freed in a brutal act in the southern Philippines that appears to have been influenced by the Islamic State group's style of killings, military and police officials said Thursday.

Army Col. Roseller Murillo said police retrieved the bodies of the two workers, who were made to wear orange gowns, in a village in Butig town in Lanao del Sur province on Tuesday.

The six workers were kidnapped by gunmen on April 5 in Butig. Four were released over the weekend after their employer negotiated with their captors, police said.

The kidnappings and beheadings have been blamed on the largely unknown Maute group of militants, who authorities say have ties with Islamic militants from Indonesia and have used black clothing with the symbol of the Islamic State group in Syria and Iraq.

The militants staged a brazen attack on an army outpost in Butig town in February, sparking a major military offensive and days of fighting that killed 24 militants and six soldiers, one of whom was beheaded.

A number of small Muslim militant factions in the south, home of minority Muslims in the largely Roman Catholic Philippines, have expressed support to the Islamic State group on online videos, but the military says there has been no evidence of any direct and active collaborations.