Twin car bombings killed six Egyptian soldiers and wounded 17 other people Wednesday in northern Sinai, where violence by Islamist militants has surged.
The blasts targeted a military intelligence building and an army checkpoint in the town of Rafah, on the border with the Palestinian-populated Gaza Strip.
No one has claimed responsibility, but the army blames Islamist militants.
Egypt's military has launched what it calls its biggest operation in years against terrorists in Sinai.
Islamist extremists took advantage of the security vacuum left when Egyptian President Hosni Mubarak was toppled from power in 2011.
Violence has surged since the military overthrew pro-Islamist President Mohamed Morsi in July.