Families of four Gaza Palestinians who were abducted in restive Sinai have called on Egypt to save their kin.

Abdul Kareem, whose nephew Yasser Zanoun was among those abducted, said on Thursday that the 25-year-old Zanoun was "much loved" and urged Egypt to help secure his freedom.

Masked gunmen stopped a bus shortly after it rolled into Sinai from Gaza late Wednesday and abducted the four men.

Gaza's Hamas rulers said they hold the Egyptian army, which is battling Islamic State militants in Sinai, responsible for the safety of the four.

But Gaza news websites have claimed the four are Hamas members and hinted at Egyptian involvement. Hamas would not comment.

It's still unclear who abducted the passengers. Initial blame pointed at Sinai militants affiliated with the Islamic State group.