Health and tourism officials said they had confirmed three deaths. A rescue worker quoted by The Associated Press said that three bodies were found at the scene, as well as the burned remains of one or possibly two other people. At least 17 of the other passengers were injured, officials said.
A spokesman for Egypt's president, Adly Mansour, called the bombing a "despicable act of cowardice directed at innocent tourists." There were no claims of responsibility, but the bombing appeared to offer worrying new evidence that militants who have been attacking Egypt's security forces for months were broadening their campaign against civilians.
Since the military ouster of Egypt's last elected president, Mohammed Morsi, in July, jihadists operating mostly in the northern Sinai have carried out hundreds of bombings, assassinations and at least one attack using a rocket-propelled grenade. The victims have included soldiers, police officers and Christian residents.
In recent months, the attacks have spread beyond Sinai to other cities as well as the heart of the capital. At least six people were killed in Cairo last month when bombs scattered around the city exploded outside a security headquarters and other buildings. A Sinai-based militant group, Ansar Beit al-Maqdis, has claimed responsibility for several of the deadliest attacks, including the downing of a military helicopter late last month.
So far, though, militants have not directly targeted Egypt's tourism industry, a source of millions of jobs in the country, as well as vital foreign currency for the government.
Egypt's tourism minister, Hisham Zaazou, said that the bus was carrying more than 30 South Korean tourists and had traveled from Cairo, to the Greek Orthodox Monastery of St. Catherine in Sinai, and was preparing to cross into Israel.
The bus had stopped to give passengers a break when the explosion occurred, parking near the Hilton hotel in Taba, where 31 people were killed in 2004 when a suicide bomber drove an explosive-laden truck into the hotel's lobby.