At least three South Korean tourists and an Egyptian bus driver were killed in a tour bus bombing in the Sinai peninsula on Sunday.
Almost all of the 33 passengers were wounded, 12 seriously, the Associated Press reports.
The strike was the first attack on tourists traveling in Egypt since former president Mohammed Morsi was ousted and the army took over in July.
The bus was reportedly headed into Israel on its way from St. Catherine’s Monastery in the south Sinai.
According to Reuters, an army source has called the bombing a terrorist attack, but no groups have claimed responsibility.
Security officials have yet to determine whether the bomb exploded inside the bus or close to it.
Since Morsi was removed from power, Sinai-based militants and supporters of the former leader are suspected in a string of attacks at security forces in the area. These attacks have largely occurred in northern Sinai, while the popular tourist areas in the south have remained mostly safe for travelers.