Al Jazeera's Amr el-Kahky, reporting from Cairo, said that it was believed that the victims could have been taken to northern Sudan across Egypt's border.
"The south of the country has been very safe, we haven't seen such events in the past few years." he said.
"The last something like this happened was in 1997, but the country's south has been very safe and every tourist convoy is escorted by policemen."
In 1997, at least 58 people were killed when armed men opened fire on foreign tourists in the ancient temple city of Luxor, just north of Aswan.