In contrast, the restive northern part of Sinai has for years witnessed attacks on security forces blamed on disgruntled local Bedouin residents. However, a fledgling insurgency by militants, some with al-Qaida links, emerged after the ouster in July of Egypt's Islamist president, Mohammed Morsi.
The 2004-2006 attacks in Sinai were the worst to target foreign tourists since the 1997 Luxor massacre, when gunmen opened fire at the Temple of Hatshepsut on the city's west bank of the River Nile, killing 58 tourists and four Egyptians.
No claim of responsibility has been made for the latest Taba bombing, which bore the hallmarks of attacks blamed on the 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.
In Seoul, the foreign ministry said in a text message that 31 passengers were from a church in Jincheon, in the country's Choongbuk Province, being led by a South Korean tour guide. Only two of its nationals were found dead and nine were injured, the ministry added.
Such discrepancies in death tolls often occur in the initial stages of an emergency response.
The Egyptian 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.
The officials spoke on condition of anonymity because they were not authorized to speak to the media.
Egypt's vital tourism sector has been badly hit by the deadly turmoil roiling the country since the 2011 revolt that deposed longtime ruler Hosni Mubarak. Sunday's attack came as signs of a slow recovery in tourism were emerging, with the focus of the rebound on Red Sea resorts in Sinai and the mainland rather on Cairo, often the scene of some of the deadliest unrest.
"I am deeply saddened by the incident," Tourism Minister Hesham Zazou told state TV.
With additional reporting by Kim Hyun-ah in Seoul