At least 12 people have been killed and 10 others were injured in Egypt's south-western desert after armed forces mistakenly opened fire on a group of Mexican tourists.

The Mexican foreign ministry said at least two of the dead were Mexican nationals. It said the victims are still being identified, and officials are working with the families of the victims.

The Egyptian ministry said police and armed forces were pursuing terrorist elements in the area and fired on four cars that turned out to be carrying tourists.

The ministry said the victims were Mexican and Egyptian.

Jorge Alvarez Fuentes, Mexico's ambassador to Egypt, and consular representatives were at the el Hospital Dar-el-Fouad in suburban Cairo. Mr Alvarez had interviewed five survivors.

Mexican foreign minister Claudia Ruiz Massieu has demanded a thorough investigation into what happened, and also called for the support of Egyptian authorities for Mexican nationals being transported to Cairo.

Egypt has been battling an Islamic insurgency in northern Sinai for years, but attacks mainly targeting the army and police escalated after Islamist president Mohammed Morsi was ousted in July 2013.
 
The tour company involved "did not have permits and did not inform authorities," according to Rasha Azazi, a spokesperson for the Egyptian ministry of tourism.
She added that any trips to the Farafra area are required to be cleared by officials.

"They were not supposed to be there," she said.