Army soldiers are seen as their convoy passes by Tahrir square to secure central Cairo as Egyptians celebrate an extension of the Suez Canal, in Cairo, Egypt, August 6.

Egypt said on Monday its security forces killed 12 people, including Mexican tourists, after mistakenly targeting their four-vehicle convoy while chasing militant extremists in the country’s Western Desert.

The vast region, popular with tourists for its oases and rock formations, is also a militant hideout. Last month the Egyptian branch of the ISIS group beheaded a young Croatian there who was working for a French company and have also launched numerous attacks against security forces.

A joint police and military operation on Sunday “chasing terrorist elements” in Wahat in the Western Desert “mistakenly” targeted four pick-up trucks carrying Mexican tourists, the interior ministry said in a statement.

“The incident led to the death of 12 Mexicans and Egyptians and wounding of 10 others,” it said.

“The area they were in was off limits to foreign tourists,” it said.

Egypt did not give a breakdown of the casualties but the Mexican foreign ministry said at least two Mexican tourists were killed.

“For the moment, we regrettably confirm the death of two Mexican nationals in this incident,” the ministry said in a statement, adding that five other Mexicans were in stable condition at a hospital in Cairo.

Mexico condemns attack

Mexican President Enrique Pena Nieto condemned the attack and demanded an investigation.

“Mexico condemns these incidents against our citizens and has demanded an exhaustive investigation about what happened from the government of Egypt,” he said on Twitter.

The ISIS group in Egypt said in a statement that it had “resisted a military operation in the Western Desert” on Sunday.

Egypt has been struggling to quell an extremist insurgency in the Sinai Peninsula, their main holdout in the country’s east, since the military overthrew Islamist president Mohamed Mursi in 2013.

Egypt, the most populous Arab country, has one of the region’s most powerful and well-equipped militaries.