Military attack helicopters rattle over the impoverished desert towns of northern Sinai and the sound of gunfire erupts nightly, raising fears among residents of a looming confrontation between Egypt's military and Islamic militants who have intensified attacks since the ouster of President Mohammed Morsi, The Associated Press reports.

Militant groups have grown bolder, striking security forces almost daily and also turning on local Christians. Some are now openly vowing to drive the military out of the peninsula on the borders with Israel and Gaza and establish an "Islamic emirate." Further fueling the turmoil is the longtime resentment among many in the Bedouin population over decades of neglect and harsh security crackdowns by the state.

The military and security forces have widened their presence, and military intelligence officials told the AP an offensive is being planned, but no further details were given.

In a rare move, the Egyptian military sent a helicopter across the border to fly over the southern end of the Gaza Strip early Friday, July 12. Egyptian security officials said it was intended as a warning to its Hamas rulers amid concerns that Gaza militants are trying to cross to back those in the Sinai. The security and intelligence officials spoke on condition of anonymity because they were not authorized to talk to the press.

Israeli security officials say their military has not taken any special precautions, but it is watching the situation carefully. They say they remain in close contact with their Egyptian counterparts, and that Egypt has coordinated its security moves in Sinai with Israel, as required by their 1979 peace treaty.

Sinai has been the most lawless corner of Egypt since the ouster of autocrat Hosni Mubarak in early 2011, with increased violence. Police stations were torched and security forces kicked out of tribal areas where they were notorious for abuses. Shootings took place regularly on police and military outposts.

But after the military deposed the Islamist president on July 3, militant groups have lashed out. In the past 10 days, at least eight security officers have been killed, the most recent on Friday. Two Christians have also died, one a priest. A gas pipeline to Jordan was bombed, ending a lull in such strikes.