Gunmen have snatched two female American tourists and their Egyptian guide near in the Sinai.
Maj Gen Mohammed Naguib, the head of south Sinai security, said the gunmen escaped in two vehicles into the mountains. A helicopter was leading a search and rescue mission.
The bus was carrying three other people who were left behind.
The tourists were returning from St Catherine's Monastery to the Red Sea resort town of Sharm el-Sheikh, reports said.
Egypt has faced deteriorating security and a surge in crime since the popular uprising that ousted Hosni Mubarak nearly a year ago. Protesters accuse the military council that has assumed power and the police force of negligence.
The unrest led to a sharp drop in the country's vital tourism sector, with revenues plunging almost 30 % last year.
The attackers were demanding the release of a number of fellow tribesmen arrested on drug trafficking and robbery charges.
Tribal leaders were mediating efforts to free the tourists, aged 60 and 65, and their guide, said Maj Gen Naguib.
He said the attackers were Bedouin tribesmen who resist government control and have been blamed for several attacks in recent months as tensions intensify between them and authorities they accuse of discrimination and of ignoring their plight.