Men carry the coffin of a soldier, killed a day earlier on the Sinai Peninsula, during a funeral in 10th of Ramadan city, north of Cairo, in July. Islamic State-affiliated militants claimed responsibility for the attack. (Fayed El-Geziry/AP)

Egyptian security forces are finding themselves increasingly bogged down in their four-year fight against an Islamic State affiliate in the northern Sinai Peninsula, despite billions of dollars in U.S. counterterrorism aid. The struggle has cost the lives of hundreds of police officers and soldiers, including at least 20 in the past week.

On Monday, at least 18 policemen were killed when a suicide bomber detonated his explosives-laden car near their security convoy. The attack, near the heavily patrolled North Sinai provincial capital of Arish, was followed by clashes as other militants opened fire, a military spokesman said.

The Islamic State affiliate, known as Wilayat Sinai, asserted responsibility for the attack, claiming that the bomber "plunged himself into six of their vehicles and blasted his car." The militants also destroyed several military vehicles, as well an ambulance and a firetruck.

Two days later, two soldiers were killed in a gun battle after militants staged a failed assault on a security checkpoint in North Sinai, a military spokesman said. Again, the Islamic State asserted responsibility.

“We see this attack that is supposedly in a completely secure area, and it claims 18 lives,” said Mohannad Sabry, the author of a book on the Islamist insurgency in Sinai. “It’s a signal that things are still not really under control.”

Similar violence has unfolded every few weeks in recent months, underscoring the insurgency’s resilience, as well as its ability to mount complex, multilayered attacks using the local terrain to its advantage.

Since July 2013, at least 1,000 members of the security forces have been killed in terrorist attacks across the restive Sinai Peninsula, according to data compiled by the nonprofit Tahrir Institute for Middle East Policy. In 2017, more than 200 members of the security forces have been killed there.

Wilayat Sinai alone has claimed more than 800 attacks across Egypt since its pledge of allegiance to the Islamic State in November 2014, said Nancy Okail, the Tahrir Institute’s executive director. Egyptian security forces, she added, have killed more than 2,500 suspected terrorists in operations in Sinai since 2013, although unofficial numbers reported by local media are significantly higher.

Although there have been fewer terrorist attacks this year than last, the number of fatalities has risen, Okail said. That suggests the militants are planning their operations more strategically and with the intent of creating maximum carnage, according to analysts.

With the Islamic State nearing defeat in Iraq and Syria, its affiliates are asserting themselves in other parts of the world, from North Africa to Afghanistan to the Philippines. The militant group, also known as ISIS or ISIL, has penetrated the mountains of Tunisia and maintains a robust presence in Libya, despite the loss of its stronghold of Sirte last year.

In northern Sinai, Islamic State-linked militants are leading the Islamist insurgency launched in the summer of 2013 after Egypt’s military overthrew the elected Islamist president, Mohamed Morsi. The coup was led by the current president, Abdel Fatah al-Sissi, and the insurgency’s stated goal is to topple his government.

The Islamic State has also increasingly targeted Egypt's Coptic Christians, who make up roughly 10 percent of the country's 94 million people. The tactic appears designed to sow further division, turning Egyptians against the Sissi government, which has failed to protect the minority community.

In 2015, the Islamic State affiliate in Sinai asserted responsibility for the downing of a Russian passenger plane after it took off from the Red Sea resort town of Sharm el-Sheikh. That attack, which killed all 224 people aboard, hit Egypt's economy hard; Russia halted civilian flights to the country, and Britain and other nations stopped airlines from flying to Sharm el-Sheikh, the source of a third of Egypt's annual tourism revenue.

Monday's attack came two months after Islamic State militants killed at least 23 soldiers at a remote outpost near Rafah, the Egyptian town bordering the Gaza Strip, in the deadliest attack on security forces in two years. Islamic State snipers have also been killing policemen in recent weeks.

This week, Egyptian lawmakers issued a statement vowing to eradicate terrorism, and U.S. State Department spokeswoman Heather Nauert said in a statement that the United States "will continue to stand with Egypt as it confronts the threat from terrorism."

Sabry and other analysts say they think the number of attacks and fatalities in the Sinai region could be much higher than the official tallies suggest. The Egyptian military has prevented journalists, local and foreign, from visiting northern Sinai, and any information released is at the government's discretion.

Sabry, who keeps close contact with Sinai tribesmen and other sources, said he has heard reports of recent attacks and clashes near Rafah. But nothing has been reported by the security forces or local media.

"It's very difficult to understand exactly what's happening," Sabry said. "There has been an intensified blackout even worse than we normally endure in Sinai."

Heba Farouk Mahfouz contributed to this report.

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