An explosion ripped through a tourist bus near a border crossing between Egypt and Israel in the Sinai Peninsula, killing at least three South Koreans and the Egyptian driver, security officials said.
The targeting of foreign tourists was the first to take place in the southern part of the Sinai Peninsula, a popular tourist area, since a fledgling insurgency by militants began to take shape in the northern part of the region following the July overthrow of the Islamist president, Mohammed Morsi.
No claim of responsibility has been made for the Taba bombing, which bore the hallmarks of attacks blamed on al-Qaida-linked militant groups battling the army and security forces in Sinai's restive north.
The security officials said the source of the explosion was not clear, but they believe it was either a car bomb or a roadside bomb that was detonated by remote control.
Rescue workers found three bodies at the scene of the attack and the badly burnt remains of one or possibly two other people, said Khaled Abu Hashem, the head of ambulance services in southern Sinai.
Almost all 33 passengers on the bus were wounded by the explosion, with 12 suffering serious injuries. The wounded were being treated in hospitals in Taba and the coastal resort towns of Nuweiba and Sharm al-Sheikh to the south on the Red Sea's Gulf of Suez.
The security officials said the bus had arrived at the Taba crossing from the ancient Greek Orthodox monastery of St. Catherine's in central Sinai. The journey, they said, originated in Cairo, Egypt's capital.