No group has said it carried out the attack
A bomb attack on a tourist bus in the Sinai peninsula has killed at least three South Korean tourists and an Egyptian driver, officials have said.
A number of South Koreans were also hurt in the attack, which came as the bus was preparing to cross into Israel.
Security sources said the bus was hit by a car bomb or roadside bomb. No-one has admitted carrying out the attack.
The Sinai peninsula has become increasingly lawless since President Hosni Mubarak was overthrown in 2011.
Officials in Sinai said the bomb blast had killed at least three South Korean tourists and the bus driver.
At least 13 other South Koreans were wounded, and were being treated in hospitals on either side of the border.
The frontier was closed after the attack.
The bus was reported to be heading into Israel from St Catherine’s monastery, a popular tourist destination near Mount Sinai.
A number of militant groups operate in the area, and Bedouin tribes live largely outside of the control of Cairo.
Attacks by Islamist militants have intensified since the army overthrew President Mohammed Morsi in July.
Mr Morsi appeared in court on Sunday to face charges of espionage and conspiring to commit acts of terror.
The Islamist former leader is facing four separate trials, three of which have now opened.