Smugglers have killed 21 Egyptian border guards near the frontier with Libya.
The attack took place in Wadi al-Gadid governorate.
Wadi al-Gadid borders both Sudan and Libya.
Local media said three smugglers were killed in clashes with the guards.
Gunmen used RPGs and heavy machine guns when they attacked the checkpoint.
The checkpoint is located in a desert area at El-Farafrah, 630km west of Cairo.
Another 10 soldiers were injured, this is the second at the same checkpoint in less than three months.
The attack came amid repeated warnings by Egyptian officials of a possible spillover of violence from across the border with Libya.
There has been relentless bloodshed over the past few months in Libya which has sparked fears of all-out civil war.