Islamist militants attacked Egypt's security headquarters in northern Sinai on Sunday with a barrage of mortar bombs and machine gun fire, security officials said.

Gunmen fired rocket-propelled grenades at the building in the town of al-Arish, prompting snipers on top of the security building to return fire. A gun battle ensued for more than an hour, witnesses said.

At least two civilians were reportedly wounded in the fighting.

Meanwhile, about 30 armored personnel carriers backed by helicopters fought militants in the town of Sheikh Zuwayed, 30 km (18.6 miles) east of al-Arish on the Mediterranean coast.

According to Palestinian news agency Ma'an, an Egyptian military helicopter was hit by a rocket-propelled grenade fired by Islamists during the incident, causing it to make an emergency landing.

Militants also attacked army checkpoints in Sheikh Zuwayed and in Rafah.

The fighting broke out after police backed by the military staged dawn raids on a number of homes in Sheik Zuwayed on Sunday. Officials said four men suspected of belonging to extremist militant groups were arrested.

On Friday, in the midst of protests across the Middle East against an anti-Islam film produced in the United States, militants waving black banners and shouting "God is great!" stormed an international peacekeepers' base in northern Sinai and battled troops, wounding two Colombians.  They stole some weapons and radio equipment, officials said.

The base near the border with Gaza and Israel houses some 1,500 members of the force, including U.S.­ troops.

Egyptian forces last month began their biggest security sweep in decades in Sinai after militants killed 16 border guards on August 5 in the most deadly attack since Egypt's 1973 war with Israel.

Since then, some 33 militants have been killed, with many more arrested.

The government sent hundreds of troops with tanks, armored vehicles and helicopters to Sinai in a joint operation with police to raid militant hideouts, arrest suspects and seize weapons.

Disorder has spread in Sinai since former dictator Hosni Mubarak was ousted in a popular uprising, with Islamist militants stepping up attacks on Egyptian security forces and the Israeli border.

Egypt's new president, Mohammed Morsi, has vowed to restore order.

Bedouin tribes in the area have long complained of neglect by the central government.