Masked assailants attacked Egyptian policemen returning from a raid in Sinai on Saturday, wounding three, a security source said.
The raid was in Sheikh Zuweid, in North Sinai, early in the morning. Police arrested two men, seized some 22 pounds (10 kilos) of marijuana and hashish, and boxes of bullets, according to the source, who asked not to be named.
On their way back, police fell under attack from assailants with a rocket-propelled grenade, the source said. The wounded were transferred to area hospital.
The violence is the latest in a string of incidents since a border attack this month and a subsequent military campaign to crack down on militants.
More than a dozen Egyptian soldiers were killed and seven others were wounded in an August 5 attack near the Rafah border crossing, when assailants with semiautomatic weapons and hand grenades stole two armored vehicles from Egyptian forces and tried to enter Israel.
Egyptian President Mohamed Morsy has visited the border with Gaza and vowed to bring justice to those affected. He dismissed several security officials and the governor of northern Sinai province in the wake of the attack.