CAIRO — Muneim (not his real name) remembers every detail of the encounter: the frightening masks; the uniforms as dark as night; the Kalashnikov rifles slung over their shoulders.

The North Sinai trader was on the road from Arish to Sheikh Zowead two months ago when he suddenly found himself face-to-face with a group of armed men. "They had their black flag with God's name on it," he recalled. "They ordered me to stop the car for a search. They finally let me go.."

Speaking softly in in a Cairo café, Muneim admits it was a close call. "A few days later an employee of the local governor's office was shot in the head on the same road," he said. "The army won't even go there."

The governor's official was the latest in growing list of victims of the Ansar Bait al-Maqdis, a terror group grappling for control of Egypt's border with Israel. Three months ago the group announced its affiliation with the Islamic State, also known as ISIS.

Two weeks ago Ansar Bait al-Maqdis fighters launched an assault on police and army installations in Arish, the chief city of northern Sinai, killing 30, mostly soldiers, and injuring dozens. Approximately 30 soldiers were also killed in October, when the group launched a carefully planned attack on a military camp near Arish. That raid, the deadliest in years, prompted Egyptian authorities to declare they would form a buffer zone on the Gaza frontier, to "eliminate the terrorists" and block secret tunnels.

Since then, the Egyptian army has intensified air raids on the fighters, destroying hundreds of homes and displacing thousands of residents the process. This is a particularly volatile zone where there is mobile phone reception and Internet only a few hours a day. A draconian curfew has just been extended for three months.

Yet these forceful moves have had just a limited impact on the militants. Experts point to last week's attack as evidence that Ansar Bait al-Maqdis is in fact becoming more sophisticated. Their operations are coordinated, "serialized," and perfectly planned. They coincide, furthermore, with the return from Syria of Egyptians who had gone to fight the Asad regime, and with the expanding influence of ISIS, whose tentacles are extending beyond Syria and Iraq.

"Ansar Bait al-Maqdis has gained experience," Sinai specialist Ismail al-Iskandarani said recently. "We have come a long way from the small, improvised attacks of four years ago."

(On Monday, Egyptian fighter planes launched raids on ISIS targets across the border in Libya after the terror group announced the execution of 21 Egyptian Coptic Christians.)

Blocking the secret tunnels should potentially limit Ansar Bait al-Maqdis's ability to obtain weaponry. In the meantime, though, the group has exploited the state of anarchy in Libya to engage in cross-border arms trafficking on that end. Its fighters also seize guns and artillery pieces (mortars, grenade launchers, AK-47 rifles) during its attacks on the regular army.

Caught in crossfire

Ansar Bait al-Maqdis, which translates roughly as "Defenders of Jerusalem," emerged in March 2011 in the disorderly period following the fall of President Hosni Mubarak. Its initial focus was Israel. Among its members were some bedouins who had suffered in the vicious search operations that followed the Taba resort bombings in Sinai in 2004.

But after the Egyptian army sacked the Islamist President Mohammad Morsi in July 2013, the group shifted its focus onto Egyptian troops. Their communiqués, issued on jihadist websites, declare their actions to be reprisals for the suppression of the Muslim Brotherhood.

Some of their methods are reminiscent of ISIS. They have begun to terrorize the local population and want to conquer territory. The heads of two bedouins — killed for supposedly collaborating with the army — were found in northern Sinai in early January.

Three months earlier, the group posted a gruesome YouTube video depicting the beheading of three other men. In the footage, the victims were forced to admit they were Israeli spies. The film showed a fourth man, allegedly an army informant, being sprayed with gunfire.

Ansar Bait al-Maqdis is invisible in Arish and Rafah, but notably present in the Sheikh Zowead area, which the army has largely abandoned.

"On many of the roads they are the law now," says Ahmad Abu Draa, a journalist in northern Sinai. "They have their checkpoints. Their grey station wagons are easily identifiable. In some villages you even see them giving out propaganda leaflets with their logo. The leaflets say "The sons of Egypt destroyed your houses. What are you waiting for to react?""

Abu Draa is one of the very few reporters working in Sinai, which is now closed to the foreign press. He says creating a buffer zone on the frontier has made things far worse as it forced many residents to leave their homes within 48 hours. "They felt they were all being punished," he says.

The pictures on his smartphone recall the worst images of war: homes crushed like wafers, streets piled high with furniture and belongings, women weeping. "The people of Sinai are caught in the crossfire," says Abu Draa. "If they collaborate with the army the militants will kill them. If they keep quiet, their homes will be destroyed."