An explosion has torn through a bus filled with South Korean sightseers in the Sinai Peninsula, killing at least four people and raising fears that Islamic militants have renewed a bloody campaign to wreck Egypt's tourism industry.
The bombing near the tip of the Red Sea's Gulf of Aqaba was the first attack against tourists in Sinai in nearly a decade.
There was no immediate claim of responsibility. But the blast bore the hallmarks of attacks blamed on the al-Qaeda-linked militant groups that have been battling government forces in Sinai's restive north for years.
At least three South Korean tourists were killed and 12 seriously wounded, according to Egyptian security officials. The Egyptian bus driver was also among the dead, the officials said.
"I am deeply saddened by the incident," Tourism Minister Hesham Zazou told state TV. The Egyptian presidency called the attack a "despicable act of cowardice" and vowed to bring the culprits to justice.
Egypt's vital tourism sector, which normally accounts for about 11 per cent of the economy and 20 per cent of all foreign currency revenue, has been badly hit by the deadly turmoil that has roiled the country since the 2011 revolt that overthrew ruler Hosni Mubarak.
Sunday's blast came as signs of a slow recovery in the industry were emerging, especially at Red Sea resorts in Sinai like Sharm el-Sheik.
Egyptian security officials said they believed the blast was caused by either a car bomb or a roadside bomb that was detonated by remote control.
Rescue workers found the remains of four and perhaps five people, according to Khaled Abu Hashem, the head of ambulance services in southern Sinai.
In Seoul, the foreign ministry said in a text message that 31 passengers from a church in Jincheon were being led by a South Korean tour guide. Two of its citizens were killed and nine wounded, the ministry added.
The discrepancy in the death toll could not immediately be reconciled.