At least Five South Korean tourists were killed and 21 others wounded in an explosion on a tourist bus in Egypt's Sinai near the Israeli border, Egyptian military and police said.
Israeli police said they heard an explosion from the Egyptian side of the Taba border crossing. The blast took place after the bus entered Egypt from Israel, security sources said.
"There is a small smoke cloud near the (border) fence, about 50 meters south of the border crossing," an eye witness said.
Emergency responders were on their way to the scene of the explosion.
Israeli police said they were preparing medics to treat any casualties from the explosion.
"The event is happening on the Egyptian side, and we are making our preparations," a police spokesman said.
Egypt has been rocked by political turmoil and violence since the army overthrew president Mohamed Morsi of the Muslim Brotherhood in July after mass protests against his rule.
Islamist militants based in the largely lawless Sinai peninsula near Israel have stepped up attacks on security forces since Mursi's downfall, killing hundreds.
Morsi appeared in court on Sunday on charges of conspiring with foreign groups to commit terrorist acts in Egypt.