A joint Egyptian police and military force has accidentally killed 12 people and injured 10, when it opened fire on them, mistaking them for militants whom they were chasing.
A tourist convoy of four 4x4 vehicles were shot at by the security force who had been chasing militants from the vast western desert which borders Libya.
At least two Mexicans were killed, Mexico's foreign ministry said in a statement.
Egyptian security forces
Egyptian security forces
Mexican President Enrique Pena Nieto condemned the attack on his Twitter account, describing it as a tragic incident and demanding a full investigation.
"Mexico condemns these deeds against our citizens and has demanded an exhaustive investigation of what has occurred," he tweeted.
Egypt's tourism ministry spokesman told the Middle East News Agency (MENA) the convoy was at an off-limits site and was using unlicensed cars. The convoy was taking part in an unapproved safari, he said.
Mexican ambassador Jorge Alvarez met with five Mexicans who were in stable condition in hospital, Mexico's foreign ministry said.
The Mexican ministry said an "undetermined" number of its country's nationals had been attacked and that it was in the process of identifying the two who had been killed.
Egypt is battling an insurgency that gained pace after the military ousted Islamist President Mohamed Morsi of the Muslim Brotherhood in mid-2013 after mass protests against his rule.
The insurgency, mounted by Islamic State's Egyptian affiliate, has killed hundreds of soldiers and police and has started to attack Western targets.