Egyptian soldiers collect the belongings of plane crash victims at the crash site in Egypt's Sinai Peninsula. (Uncredited/Russian Ministry for Emergency Situations photo via AP)

– Egypt’s Sinai Peninsula was long known for its stunning desert treks and pristine diving. But in recent years, the territory has gained a reputation for its violence and militancy.

Some of the same arid landscapes that drew tourists for desert safaris are now lawless badlands stalked by dangerous militant groups linked to al-Qaeda and the Islamic State. Egypt’s government has deployed troops, tanks and fighter jets to the peninsula’s volatile north to combat an insurgency, but so far it has failed to quell the violence.

On Saturday, when a Russian airliner plummeted to the ground in a remote area of Sinai, a local Islamic State affiliate known as the “Sinai Province” asserted responsibility for the crash. The disaster killed all 224 people on board, but aviation and security officials say there is no evidence the plane was brought down by terrorism.

The Sinai-based militants do not possess the type of advanced weapons necessary to hit high-flying aircraft, defense analysts say. But the militants’ acquisition of increasingly dangerous weapons, and a growth in sophisticated insurgent attacks, has raised serious concerns about their ability to strike high-profile targets.

In recent years, the insurgency has transformed from a coterie of homegrown jihadists based in northern Sinai into a dangerous Islamic State offshoot capable of staging complex attacks on the Egyptian mainland, including in Cairo, the capital. The militants, who include veteran foreign fighters, have survived a string of military offensives in North Sinai, running their own checkpoints, planting roadside bombs and flaunting their expanding weapons stocks.

The militants have launched thousands of mostly small-scale attacks on security forces since a military coup against Islamist President Mohamed Morsi in 2013, according to independent tallies of armed incidents. Militant cells linked to the Islamic State and al-Qaeda are believed to have been behind a series of car bombs detonated in Cairo this summer. In a particularly alarming attack — one that analysts say required an intricate level of planning — a car bomb killed Egypt’s top prosecutor, Hisham Barakat.

In a recent video posted on jihadist forums, Sinai Province broadcast footage of its fighters training with and firing at least one shoulder-fired antiaircraft system, a weapon Israeli officials said was likely a Russian-built SA-18 Igla, which can hit aircraft flying at a maximum of 11,000 feet. In January 2014, the militant group that later pledged allegiance to the Islamic State released a video of a fighter shooting down an Egyptian military helicopter with a shoulder-fired missile, sending the aircraft tumbling in a ball of orange flames.

The U.S. Federal Aviation Administration “has long warned U.S. airlines against flying over the Sinai because of the risk of hazards from extremists,” said James Record, a former commercial airline pilot and an aviation professor at Dowling College in New York. The agency’s latest warning, he said, “advised airlines to fly at least 26,000 feet above Sinai to stay out of range of antiaircraft weapons.”

This summer, Sinai Province published dramatic images of what appeared to be a missile or rocket slamming into and destroying an Egyptian navy frigate off the coast of North Sinai, an attack the military later confirmed.

Defense industry publication IHS Jane’s said the militants could have used a Russian-made 9K129 Kornet antitank guided missile system to attack the ship. At the time, according to Jane’s analyst Jeremy Binnie, the Kornet had been used by Palestinian militant groups in the Gaza Strip but had not “previously been seen in the hands of Sinai-based Sunni militants.”

The rise in complex attacks and the use of advanced weapons have raised fears of the jihadist threat to civilian aircraft in Egypt, whether from ground fire or an attempt to sabotage or plant explosives on a commercial airliner.

The militants have used North Sinai, for years a thoroughfare for weapons trafficking and other criminal activities, to build support and strengthen their ranks. But the southern part of Sinai, which boasts a long stretch of Egypt’s Red Sea coastline, is crucial to the country’s tourism industry — and a prime target for the militants, experts say.

It was there that the Russian passengers had been vacationing before boarding their ill-fated flight to the Russian city of St. Petersburg.

“The Islamic State has so far focused on acquiring territory and grasping at the trappings of statehood rather than acting like a traditional terrorist organization,” said Jens David Ohlin, a professor of international law and security expert at Cornell University.

“If indeed the airliner was brought down by ISIS, this would represent a new and dangerous development,” he said, using a common acronym for the Islamic State. “ISIS combining the bloodiest aspects of statehood and terrorism into one dangerous mess."

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Today’s coverage from Post correspondents around the world

Heda Habib contributed to this report.