Security in the isolated desert region has deteriorated since the overthrow of President Hosni Mubarak in a popular uprising last February. South Sinai's Red Sea coast is a major tourism hub for Egypt.
The two tourists were among a party of five traveling from Saint Catherine's monastery in central Sinai to the resort town of Sharm el-Sheikh when a vehicle carrying men armed with machine guns stopped their small bus, the sources said.
The gunmen first took all the tourists' money and valuables and then, as an apparent afterthought, grabbed the two women, forced them into their vehicle and fled into the mountains, the security officials said.
Two army and police search parties had gone into the area to try to track them down, the officials said.
Bedouin in the Sinai, who complain of neglect and discrimination by the authorities in Cairo, have attacked police stations and blocked access to towns to show their discontent and press for the release of fellow tribesmen from prison.
Last month, Bedouin seized 50 German and British tourists whose coach accidentally crossed a roadblock they had set up as a protest against the governor of South Sinai.
Those tourists, who were also on a trip to the monastery, were released a few hours later.
Four armed men also attacked a hotel in an Egyptian Red Sea resort popular with Israeli holiday makers last month before fleeing when police returned fire.