An attack on a tourist bus in the Red Sea resort town of Taba killed at least four on Sunday.
It is the first attack on tourists during a terrorist campaign that has rocked the country since the ouster of Islamist president Mohamed Morsi in July 2013.
Three Korean tourists and the Egyptian bus driver were killed, while 14 others were injured in the blast on Sunday afternoon, security sources told Al-Ahram's correspondent in South Sinai.
Earlier, security sources had told Al-Ahram Arabic news website that the bus was targeted by a missile.
However, South Sinai governor Khaled Fouda told private satellite channel CBC TV that the blast resulted from an explosive device planted on the bus.
Fouda stressed that investigations are still underway: "Until they are over, we cannot be sure of the cause of the explosion."
The explosion damaged the front of the bus, the interior ministry said.
The bus was on route from Saint Catherine to Taba where it was hit by the blast near the Taba crossing.
People and security officials walk and look as smoke rises from a tourist bus in the Red Sea resort town of Taba in the south Sinai, February 16, 2014 (Photo: Reuters)
Most casualties were taken to Taba and Nuweiba hospitals, Ahram Arabic reporter Hani El-Asmar said. While the urgent cases were taken to Sharm El-Sheikh International Hospital.
Embassies can transfer their nationals via airplane if needed, Tourism Minister Hisham Zaazou told CBC.
Thirty tourists of various nationalities were on the bus when it was attacked.
The authorities have closed off the international road leading to Taba to search for the perpetrators.
Seoul is in constant contact with the Egyptian authorities, Foreign Ministry spokesman Cho Tae-young told the Korean Times.
A pattern of bombings and assassination attempts has been growing since Morsi's ouster.
The main targets have been police and military installations in the Sinai Peninsula.
There have also been an increasing number of attacks in Cairo and the Nile Delta region in recent months.
Ansar Beit Al-Maqdis, an Al-Qaeda-inspired Islamist militant group based in Sinai, has taken responsibility for many recent attacks in Egypt.
The last major attack on tourists in Egypt took place in 2006 when a bomb killed 23 people in Dahab in South Sinai.
In 2005, 88 people died in a bomb attack in Sharm El-Sheikh, an hour drive from Dahab.
In 2004, 34 people died and 135 were injured in a terrorist blast in Taba.
The Egyptian tourism industry, once worth more than a tenth of the country's economic output, has been struggling to recover since the 2011 revolution.
It has suffered further blows since last summer's political upheaval, which saw Islamist president Mohamed Morsi ousted after mass protests against his rule.
Egypt welcomed around 8.7 million tourists in the first eleven months of 2013, compared with 10.5 million in the same period of 2012.
In October 2013, Zaazou said that Egypt aimed to attract 13.5 million visitors in 2014, to bring in around $11 billion.