Gaza's Hamas rulers say gunmen abducted four Palestinians in neighboring Sinai after intercepting a bus bound for Cairo airport.

The Hamas interior ministry said the Palestinian travelers had crossed from Gaza into Egypt late Wednesday on the third day of the partial opening of Rafah crossing point.

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.

Hamas officials are trying to determine who the gunmen are.