The death toll from the attack on a mobile checkpoint in Arish, capital of restive North Sinai province, has risen to seven policemen after two conscripts died Thursday morning of their injuries, a security source told dpa.
Gunmen had opened fire on security forces in central Arish late Wednesday, killing five policemen, including three officers, and injuring four conscripts. Two of the injured died hours later, the source explained.
Sinai Province, the Islamic State affiliate in Egypt, claimed responsibility for the attack.
In a statement circulated on Twitter, the terrorist group said that three of its members carried out the operation and then withdrew from the scene after they had seized an armoured vehicle and weapons.
The group claimed it had killed nine police officers.
The statement could not be independently verified by dpa.
Previously known as Ansar Bayt al-Maqdis, Sinai Province first appeared in September 2011 and rebranded itself with an Islamic State pledge of allegiance in November 2014.
Security forces in the largely desert Sinai peninsula have come under repeated attacks from hardline jihadists since the 2011 uprising that toppled long-time dictator Hosny Mubarak. The extremists stepped up their attacks after the military deposed Islamist president Mohammed Morsi in 2013, killing scores of security personnel.
The violence has mostly occurred in North Sinai, prompting authorities to set up a kilometre-deep buffer zone there along the Gaza border.