CAIRO — A series of simultaneous bombings targeting security facilities in the Sinai killed at least 26 people Thursday night, prompting fears that the Egyptian government’s campaign of home demolitions, curfews and sweeping arrests has failed to choke off a budding insurgency there.

The wave of bombings was the first major outburst of violence since the main Islamist militant group operating in the Sinai pledged allegiance to the Islamic State in November.

Through a Twitter account linked to the group, now known as the Sinai Province of the Islamic State, it claimed responsibility for the attacks on more than a half-dozen locations.

The assault, involving nearly simultaneous bombings in several places around the cities of Arish and Rafah, was the most complicated and widely coordinated terrorist attack in Egypt in years. It was also the deadliest attack in the Sinai since a multistage assault on a military checkpoint killed at least 31 people on the night of Oct. 24.