The northern Sinai Peninsula, long a relatively lawless zone, has become a dark harbinger of what could follow elsewhere in Egypt if the interim government cannot peacefully resolve its standoff with the Islamist protesters camped out in Cairo. 

In the five weeks since Egypt’s military ousted the Islamist president, Mohamed Morsi, the endemic violence here has spiraled into something like an insurgency, with mysterious gunmen attacking military and police facilities every night. 

Last week, the violence threatened to draw in Israel. On Thursday, Israel briefly closed an airport at the Red Sea resort of Eilat after Egyptian officials warned about the possibility of militants firing rockets from Sinai. The next day, up to five suspected militants were killed and a rocket launcher was destroyed in an airstrike in Sinai, the state news media reported, and there were unconfirmed reports that Israel had carried out the strike. 

The Sinai attacks have taken about 62 lives, officials say, not counting the 60 suspects the Egyptian authorities claim to have killed. There has also been a troubling rise in attacks on Christians, who are fleeing the area in large numbers. 

Although the world’s attention has been focused on Cairo, where about 140 Islamist Muslim Brotherhood supporters have been killed in clashes with the police since Mr. Morsi’s ouster, the chaos in Sinai in some ways represents a more troubling prospect. Unlike the Brotherhood, which has a longstanding commitment to nonviolence, the jihadists here are out for blood, and they appear to have been energized by the military’s reassertion of power. Some Egyptians fear a renewal of the kind of terrorism they suffered during the 1990s, especially if the military resorts to an even broader and more forceful crackdown. 

The northern Sinai may be both a symptom and a cause of Egypt’s festering crisis: one of the military’s reasons for ousting Mr. Morsi was the belief that he was too soft on the jihadists here and saw them as potential allies. Yet the military, for all its warlike talk, seems unable to thwart the mysterious bands of gunmen who own the night here. 

“We are living in a state of constant terror, but we see nothing from the police or the army,” said Mitri Shawqi Mitri, a 53-year-old Christian shopkeeper whose son, Mina, was kidnapped by gunmen early this month. “Everything has stopped for us, there is no work, all the churches have closed, the priests have fled.” 

Like many Christians living in Sinai, Mr. Mitri plans to leave, and a wall of his modest house in the town of El Arish has the words “For Sale” scrawled on it in Arabic. At least one Christian priest here has been killed in the past month, and several Christians have been kidnapped, including two women and Magdy Lamy, the shopkeeper who was beheaded. Many others have received death threats from militant Islamists warning them to leave Sinai, Mr. Mitri and other local Christians said. 

As Mr. Mitri sat talking to a reporter in his home, he received a text message from the kidnappers, who were demanding a ransom of 150,000 Egyptian pounds, about $21,500. “They want to know if I have the money in the house with me,” he said, his face creased with anger and fear. 

The military announced last week on its Facebook page that its counterterrorism operation over the past month in Sinai had led to 103 arrests, and the destruction of 102 tunnels, 40 underground fuel storage tanks and 4 houses used by extremists. The reference to tunnels, presumably those used to smuggle weapons and goods into Gaza, tallies with the military’s routine suggestions that Hamas, the Palestinian militant group that controls Gaza, is involved in the violence. However, there is no evidence to suggest that is true. 

Most residents here say the authorities appear to be on the defensive, with soldiers and the police hunkered down at their posts and suffering daily casualties. 

Although the attackers mainly hit the police and the military, a dozen civilians have been killed in the cross-fire and many others have been wounded, according to local hospital officials. Hanny Aish, a worker at a cement factory, was on a bus in the wee hours of July 15 when a rocket-propelled grenade crashed through the window, killing 3 of the 20 people on board and wounding the rest. 

“I was sitting behind the driver, and all of a sudden I had flesh and blood all over me,” Mr. Aish, who suffered glass cuts across his body and shattered eardrums, said during an interview at his home. 

The attackers’ target appears to have been an armored vehicle that passed by just afterward. But as in the rest of Egypt, even the most basic perceptions of the conflict reflect a bitter division between supporters and opponents of Mr. Morsi. The first group tends to blame the military for all the recent attacks here, saying it is staging fake jihadist attacks to build a pretext for a future crackdown. 

Sameh Muhammad, a conservative Muslim whose brother Salem was killed in the same bus attack in which Mr. Aish was wounded, said he believed an Egyptian military jet had fired a missile at the bus — despite the testimony of witnesses like Mr. Aish and photographs that appear to show that the bus was struck from the side. 

“We heard that a witness saw the jet firing a rocket at the bus,” said Mr. Muhammad, a religious teacher dressed in a white skullcap and gown, with the long, scraggly beard of a hard-line Salafist Muslim. “They always say that Islamists have done this kind of crime,” he said, as a pretext “to crack down on the whole movement.” 

Jihadism has long been a problem in Sinai, which was under Israeli occupation from 1967 to 1982. The area’s independent Bedouin tribes have resisted full integration into the state, and smuggling and drug trafficking to neighboring Israel and Gaza have been rampant here for decades. 

But the Egyptian state has contributed to the problem, local leaders say. “They treated us all as traffickers and criminals, and this marginalization made a fertile ground for terrorism,” said Sheik Abdelhadi Etaik Sawarka, a leader of one of the area’s main tribes. 

After the 2011 revolution in Egypt, the security services withdrew from Sinai, leaving a vacuum where armed Islamists thrived, and some foreign fighters filtered into the area. The militants also gained access to more sophisticated weapons from Libya after the civil war in that country, analysts say. 

There are persistent rumors that the fighters have acquired surface-to-air missiles that could threaten aircraft in Egypt and Israel, though these have not been confirmed. 

The identities of the attackers in Sinai remain mysterious: no one has claimed responsibility, and the Egyptian authorities have said little about them, helping to fuel conspiracy theories. But “it appears that Islamist militants are taking advantage of a fluid situation,” said Michael Wahid Hanna, an expert on Egyptian politics and the military at the Century Foundation. 

The biggest concern for the United States and Israel, Mr. Hanna added, is “the possibility that Egypt has lost control over what’s going on in the Sinai.” 

Some Islamists and Bedouins here claim that Mr. Morsi’s administration was a welcome relief from the heavy-handed approach of Hosni Mubarak and his predecessors. But the change was mostly a matter of tone. Mr. Morsi ordered a crackdown on the jihadists, especially after 16 soldiers were killed by gunmen at a Sinai military base last August, though the subsequent military campaign was short and yielded few results. 

All the Islamic groups with an official presence here deny responsibility for the recent violence. But some of the more conservative Islamists also talk with a certain confidence about their situation, as if they held a trump card. 

“If the military pushes the Brotherhood down here, it will have to push all the Islamic groups down, because they are all supporting the Brotherhood,” said Sheik Asaad el-Bayk, a Shariah court judge and a leader in a new hard-line Islamic movement called People of the Sunna and the Community. “They cannot do that, because it would mean major violence.”