The Egyptian military has said that 25 armed fighters have been killed and injured during an overnight raid in its northern Sinai peninsula.
Ahmed Ali, a spokesman for Egypt's military, said on Sunday that a weapons depot was also destroyed during the helicopter assault, south of Touma village in Sheikh Zuwaid city in North Sinai.
Ali said that the depot "was being used for terrorist acts against the armed forces and police, terrorising the innocent citizens of North Sinai".
He did not offer a breakdown of casualties, but sources said at least 12 people were killed.
He said that the military and police forces would continue to chase the fighters until security and stability was restored in North Sinai and all around Egypt.
Security sources told Al Jazeera on Sunday that six people were arrested during the raid.
The assault follows an air strike by the Egyptian military on Friday, which killed four people.
The armed group, Ansar Beit al-Maqdis, had earlier said Israeli drones were behind the attack and accused the Egyptian army of co-ordinating it with the Israelis.
A funeral was held for the four killed fighters on Saturday, with their bodies being driven through several border towns in Sinai.
Dozens of men on pick-up trucks flying their black flag paraded through the towns, in an act of defiance to the army, witnesses said.
"Our heroes became martyrs during their jihadi duties against the Jews in a rocket attack on occupied lands," Ansar Bayt al-Maqdis said on its website.
Fighters based mainly in the northern Sinai near Israel's border have escalated attacks on security forces and other targets since July 3, when the army ousted President Mohamed Morsi and installed a new government in Cairo.
But the army has been reluctant to confront the fighters inside towns in order not to provoke the tight-knit tribes, military sources said.
Egypt and Israel have co-operated in tackling armed groups in Sinai in the past.