Islamic State's Egyptian affiliate claimed responsibility on Thursday for a bombing that the army said killed four soldiers near Rafah, a town on the border with the Gaza Strip.
Egypt is battling an increasingly brazen insurgency in the Sinai Peninsula that has killed hundreds of police officers and soldiers since the army toppled Islamist President Mohamed Mursi in 2013 after mass protests against his rule.
The militant group Sinai Province, which has pledged allegiance to Islamic State, said in a statement posted on Twitter that it had planted the bomb on the road between Rafah and the town of Sheikh Zuweid.
Reuters could not independently verify the authenticity of the statement.
The Egyptian military had earlier said in a statement that an army officer and three soldiers were killed in the attack.
President Abdel Fattah al-Sisi has said militancy poses an existential threat to Egypt, the most populous Arab country.
Sinai Province last week claimed responsibility for a rocket attack on an Egyptian naval vessel near the coast of Israel and Gaza, less than a week after claiming a bombing in Cairo that heavily damaged the Italian consulate.
The group earlier this month assaulted several military checkpoints in North Sinai, in what was the fiercest fighting in the region in years.
