Egyptian military helicopters carried out a second day of air raids on Sunday in the Sinai Peninsula, where they are facing an insurgency by Islamist militants, witnesses said.
Apache helicopters hit targets in north Sinai near the Rafah border crossing with the Hamas-ruled Gaza Strip, witnesses said.
The army said nine "radical Islamists" were killed on Saturday in north Sinai when it launched an air and ground offensive in which nine suspects were also arrested and three arms caches destroyed.
On Saturday, security officials gave a toll of 10 killed, 20 wounded and 15 arrested.
The military has been facing an insurgency in north Sinai, a haven for Al-Qaeda-inspired militants who have launched almost daily attacks against security forces in recent weeks.
Deadly violence has grown in the Sinai since former president Hosni Mubarak was toppled in massive popular protests in 2011.
The restive region has seen an increase in clashes between militants and security forces since the military toppled Islamist president Mohamed Morsi on July 3 in a popularly backed coup.
For years Sinai has defied the central government's authority with its Bedouin population complaining of poverty and discrimination.
The surge in militant attacks there and elsewhere around the country has raised fears of a revival of the Islamist insurgency that plagued Egypt in the 1990s.
The army on Tuesday launched intensive strikes in the Sinai which a security source described as the "biggest aerial assault of its kind" in the peninsula.
On August 19, militants killed 25 policemen in the Sinai, in the deadliest attack of its kind in years.
The army says it has killed around 100 Islamists in Sinai over the past two months when violence surged and says the militants killed 58 policemen, 21 soldiers and 17 civilians in the region.
The figures cannot be independently verified as the military denies media access to the combat zones.