Maj. Gen. Mohammed Naguib, the head of south Sinai security, said the gunmen were driving a sedan and a pickup truck. Naguib said the abductors sped away into the mountains. A helicopter was leading a search and rescue mission, he said.
The bus was carrying three other people who were left behind, Naguib said. Their nationalities were not immediately known.
The tourists were returning from the monastery to the Red Sea resort town of Sharm el-Sheikh, according to the state newspaper Al-Ahram.
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 percent last year.
Tourism Minister Mounir Abdel-Nour said last month that the number of tourists who came to Egypt in 2011 dropped to 9.8 million from 14.7 million the previous year. Revenues for the year clocked in at $8.8 billion compared to $12.5 billion in 2010.
