South Korea has voiced shock and outrage at the bombing of a tourist bus in Egypt that killed three of its nationals, while issuing a travel ban for the Sinai region.
The bomb struck the bus carrying 31 South Korean tourists and their guide near an Egyptian border crossing with Israel in South Sinai on Sunday.
The Egyptian bus driver was also among the dead, Egyptian officials said.
Another 13 were injured in the attack, for which no one immediately claimed responsibility.
"We are shocked and enraged at the terrorist bombing on the bus ... and strongly condemn the act," South Korea's Foreign Ministry said in a statement on Monday.
Three South Koreans - two men and a woman - were killed along with the Egyptian driver, the South Korean Foreign Ministry confirmed.
The tourists were all members of the same church group from the central South Korean county of Jincheon who were on a 12-day trip through Turkey, Egypt and Israel.
"We believe that terrorism can never be justified under any circumstances and such inhumane and unethical acts should be weeded out by all means," the South Korean Foreign Ministry said.
The Egyptian president's office called the attack a "despicable act of cowardice" and promised to bring the culprits to justice.
"I am deeply saddened by the incident," Hesham Zazou, Egypt's tourism minister, told state TV.
It was the first attack on tourists in Egypt since the overthrow of President Mohamed Morsi by the army in July led to civil unrest and a spate of attacks that have mainly targeted security forces.
The bus had arrived at Taba from the ancient Greek Orthodox St Catherine's monastery in central Sinai.
Jean Antoine of Craft Tours, the company which owned the bus, told Al Jazeera that the bomb was planted under the driver's seat inside the bus. He said the vehicle had been parked outside the monastery the previous night.
The tourists were waiting at the crossing to enter Israel when the explosion happened, the Egyptian Interior Ministry said.
An Israeli police spokesman confirmed that the bus was on its way to Israel. The victims will be treated in Egyptian hospitals, but Israel has dispatched medical teams to the border.
Kim Young-So, South Korea's ambassador to Egypt, told Seoul's MBN TV station that the bombing appeared to be a suicide attack.
"An Egyptian man in his 20s suddenly boarded the bus and detonated the bomb ... it appears to be a suicide bombing by a terrorist," Kim said.
South Korea issued a total travel ban on the Sinai region and the Gulf of Aqaba, while urging its nationals living elsewhere in Egypt to take extra precautions or leave to a third country if possible.
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-Sheikh.
Egypt's vital tourism sector, which normally accounts for about 11 percent of the economy and 20 percent of all foreign-currency revenue, has been badly hit by the deadly turmoil that has gripped the country since the 2011 revolt that overthrew President Hosni Mubarak.
Nick Shifrin, reporting from Jerusalem, said the attacks were a major turning point for the armed groups operating in Sinai.
It was the first attack against tourists in Sinai's southern region since a spasm of bloodshed in 2004-06 that killed about 120 people.
That included a bombing at a luxury hotel in Taba in 2004 that left 34 people dead, 11 of them Israelis.
The attack has raised fears that a deadly campaign against tourists similar to one waged in the 1990s by extremists may have resumed.
In 1997, armed men opened fire at the Temple of Hatshepsut in the city of Luxor, killing 58 tourists and four Egyptians.