MANILA, Philippines – Armed men stopped a van in Lanao del Norte, robbed its passengers and murdered four Christian male passengers execution-style, police said Tuesday.

They said a fifth also taken off the bus was missing.

Police and military sources said the killings took place in an area known to be a stronghold of the Moro Islamic Liberation Front (MILF).

They would not say whether the men were targeted because of their religion or whether the gunmen were Muslims.

The bus was carrying about 15 people when it was stopped near Malabang town on Monday, said regional police spokesman Supt. Danilo Bacas.

The passengers were robbed but the women were allowed to leave unharmed.

Four of five Christian men who were dragged into a forest were later found shot in the head at close range while another remains missing, Bacas said.

The 12,000-member MILF guerrilla group signed a ceasefire with the government in 2003 to open the door for peace talks, but sporadic clashes still occur.

Bacas, spokesperson of the Autonomous Region in Muslim Mindanao (ARMM) police, said the van – with about 15 passengers – was heading for Pagadian City when stopped by gunmen on board a Tamaraw FX in Barangay Montay in Malabang, Lanao del Sur around 4:30 p.m.

“At gunpoint, they separated the men from the women,” Bacas said.