The military said it had killed 10 “extremely dangerous” extremists, in addition to 28 jihadists it had previously announced as having been killed.
A statement added that 400 “criminal elements and suspects” had been arrested, having previously announced the arrest of 126 people.
The dead militants had been “hiding inside a house in the vicinity of El-Arish city (North Sinai province’s capital) following a shoot-out,” spokesman Col. Tamer Al-Rifai said in the statement.
The operation has also destroyed several vehicles and warehouses, he said.
On Friday, the military announced the start of “Operation Sinai 2018” in the Sinai Peninsula bordering Israel, the central Nile Delta and the Western Desert near the border with Libya.
The security sweep comes as President Abdel Fattah El-Sisi seeks re-election in March, after a first term in office that has seen him crack down on an insurgency and other opponents.
Egypt’s security forces have been increasingly targeted by militants since the army — then headed by Sissi — overthrew president Muhammad Mursi in 2013.
Militants linked to Daesh and based in North Sinai have waged a deadly insurgency against the country’s security forces.
Egypt’s air force and navy have also been taking part in the operation, with the Sinai sweep focusing on targets in the north and center of the peninsula.