Thirteen soldiers were also wounded.
The rebels say they are acting in response to the bloody repression launched by the authorities after Morsi’s overthrow, which has seen at least 1,400 people killed and thousands more jailed.
News agencies are reporting that ISIS said that the rockets had been in retaliation for the support Israel gave to the armed forces of Egypt on Wednesday after militants had attacked a number of checkpoints the Egyptian army had set up in northern Sinai.
The insurgency, aimed at toppling the Cairo government, has intensified since the army ousted Islamist president Mohamed Mursi after mass protests against his rule in 2013.
Courts have sentenced hundreds to death, including Morsi, who was convicted of involvement in attacks on police stations.
As a safety precaution, the Israeli military has closed a southern highway which runs through the Egyptian border.
Combat operations continued in the area late Saturday, with the Egyptian army saying Apache attack helicopters fired missiles at groups of extremists, killing 10 of them. Tuesday, President el-Sisi trumpeted his desire to bring ISIS to its knees.
The judiciary is restricted by laws, and swift justice is also restricted by laws. El-Sissi has not addressed the public since the Sinai battles erupted.
Soldiers, policemen, civilians and militants were among the dead.
The Islamic State jihadist group mostly operates in Iraq and Syria, but it is also known to have affiliates in North Africa, Yemen, Pakistan and Afghanistan.
ISIL-linked militants claimed they launched three rockets towards southern Israel from Sinai on Friday. The Brotherhood responded by calling for a “rebellion”, raising the prospect of a further uptick in violence.
Spokesman, Brig. Gen. Mohammed Samir released graphic pictures on his official Facebook page showing the camouflage-clad corpses of what it said were militants involved in the attack.
Witnesses said remains of the jihadists were still sitting in vehicles pulverized by the Egyptian military, adds the NYT.
“This incident is a game-changer”, an official told Reuters on condition of anonymity.
“So long as the Egyptian army is present, no one will be able to terrorize Egyptians”, a confident al-Sissi said.