BEIRUT — The Mexican government on Monday demanded an explanation for an apparently mistaken attack by Egyptian forces that killed 12 members of a tourist convoy in the desert southwest of Cairo.

Two Mexicans were among the dead in the assault Sunday in the isolated Al Wahat area, which apparently occurred when Egyptian forces mistook the tourists for a group of militants, officials in the two countries said. Ten people were reported injured, six of them Mexican.

Mexican President Enrique Pena Nieto condemned the attack, and demanded that the Egyptian authorities conduct a thorough investigation.

The Mexican government also said that Mexico’s ambassador to Egypt, Jorge Alvarez Fuentes, had spoken to the injured Mexican victims at the hospital where they were being treated. It said another top official from the Foreign Ministry had been dispatched to Egypt to help support those affected by the tragedy.

“The Mexican government asks the Egyptian authorities to give this matter the highest priority and urgency,” Foreign Secretary Claudia Ruiz Massieu said at a news conference in Mexico City. She added that Egyptian authorities had agreed to carry out a full investigation.

While details were still vague, it appeared from official and media accounts that Egyptian authorities suspected that a four-vehicle convoy carrying tourists in the western desert was actually ferrying insurgents active in the zone.

The desert expanse has long attracted foreign sightseers, though tourism in Egypt has plummeted in recent years because of security concerns.

The group of Mexican tourists had arrived in Cairo on Sept. 11, according to Ruiz Massieu. Two days later, she said, they left the capital to visit the Bahariya Oasis, and came under attack from “bombs launched from airplanes and helicopters” when their tour bus stopped at the side of the road for a break.

There were conflicting reports about whether the area where the incident occurred was officially open or closed to tour groups.

In an interview with Mexican radio, Araceli Rangel Davalos said her sister and cousin were on the trip and the cousin, Rafael Bejarano Rangel, was among those killed. According to Rangel Davalos, they were among 15 people from Guadalajara, some of whom had made the same trip before with the same guides.

She called it “a terrible mistake” for them to have been traveling in the area. In the past, she said, “Whenever they traveled there they always had the right permits. I don’t know what happened.”

“But,” she added, “I knew the guide and they had never exposed us to any danger before.” She said the guide was among those killed.

The nationalities of the non-Mexican victims were not immediately made public.