GAZA CITY, Gaza Strip — Gaza’s Hamas rulers say gunmen abducted four Palestinians in neighboring Sinai after intercepting a bus bound for Cairo airport.

Interior ministry spokesman Iyad Bezem said in a statement that the kidnapping took place late Wednesday night in the troubled northern Sinai region as the bus headed for the Rafah border crossing into Gaza.

He said that his ministry had contacted its Egyptian counterpart “to establish the circumstances of what happened and demand that the Egyptians work to protect the victims and release them”.

Witnesses told The Associated Press that several masked militants opened fire in the air and stopped the bus half an hour after it rolled into the restive peninsula. They grabbed four youths and fled the scene.

The witnesses — Palestinians who were in the bus — preferred not to disclose their names fearing retribution. They said they believed the militants to be from the Egyptian affiliate of the Islamic State group.

Officials said that some of the passengers who arrived safely described the assailants as wearing “Pakistani-type” clothes and holding laptop computers on which they checked passengers’ names before separating the four from the group and taking them away.

Hamas officials are trying to determine who the gunmen are.

North Sinai, where Egyptian security forces are fighting an Islamist insurgency, is a bastion of the Egyptian affiliate of the jihadist Islamic State (IS) group, which is spearheading an insurgency that has swelled since the army’s ouster of president Mohamed Morsi in July 2013.

Formerly known as Ansar Bayt al-Maqdis, the key jihadist group in the region changed its name to “Sinai Province” when it pledged allegiance to IS in November.