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.
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.
Heba Farouk Mahfouz contributed to this report.