At least 18 policemen have been killed and three injured on Monday in a terrorist attack claimed by the Islamic State in North Sinai's city of Al-Arish.
Seven others were wounded in the attack, said security and military officials.
Militants detonated a roadside bomb near the town of el-Arish, reportedly destroying three armoured vehicles and a fourth with signal-jamming equipment.
The assailants, whose identities were not yet known, later opened fire at survivors and commandeered a police pickup truck.
Among those killed were two police lieutenants. The wounded included a police brigadier general, according to the officials, speaking on condition of anonymity because they were not authorized to brief media.
One source said authorities received a tip off about the hideouts of the individuals, who they suspect of being members of Hasm, a group which has claimed several attacks around the Egyptian capital targeting judges and policemen since previous year. State news agency MENA quoted a high ranking ministry official confirming the attack and casualty figures.
Egyptian police say they killed 10 suspected militants in a shoot-out near Cairo Sunday. According to the military, thousands of militants have been killed in the operations held against them.
In recent years there has also been a wave of attacks, mainly targeting security forces, blamed on splinter factions of Morsi's Muslim Brotherhood group.
The ambush came a day after authorities said they had caught a cell planning attacks in the capital, Cairo.
A statement by the Interior Ministry, which oversees security forces, said the militants were hiding in two apartments in the densely populated Ard el-Liwa neighborhood, where they held organizational meetings and planned a "series of terror attacks" in central provinces, a reference to Cairo and its twin city of Giza.