Shaimaa Sabbagh.

CAIRO — Twenty-five people were killed in a bomb attack on military buildings in the capital of Egypt’s restive North Sinai province on Thursday, while an army major was shot dead at a checkpoint in Rafah near the Gaza Strip, medical and security sources said.

The flagship government newspaper, al-Ahram, said its office in the town of Al-Arish, which is situated opposite a military hotel and base that security sources said were the intended targets of the bombing, had been “completely destroyed.”

Later, suspected militants killed an army major and wounded six others at an army checkpoint in Rafah, security sources said.

An Islamist insurgency based in Sinai has killed hundreds of security officers since president Mohamed Morsi of the Muslim Brotherhood was removed from power by a military coup following mass protests against his rule.

Tensions have also been raised across Egypt this week by protests, some of them violent, marking the anniversary of the 2011 uprising that ousted veteran autocrat Hosni Mubarak.

Earlier on Thursday, a group of women protested in Cairo against the death of activists Shaimaa Sabbagh and around 25 others allegedly killed by security forces at rallies commemorating the 2011 uprising.

Sabbagh, 32, died on Saturday as riot police were breaking up a small, peaceful demonstration. Friends said she had been shot and images of her bleeding body rippled out across social media, sparking outrage and condemnation.

“The Interior Ministry are thugs!” chanted around 100 female protesters gathered at the site of Sabbagh’s death. Some held up signs with the word “murderer” scrawled over the face of Interior Minister Mohamed Ibrahim.

The protesters were defying a law that severely restricts protests. “People are here at incredible risk to themselves. But it’s a way of standing against the fear they have instilled,” said activist Yasmin el-Rifae.

Ibrahim has said an investigation into Sabbagh’s death will lead to prosecution if any member of the security forces is found responsible.

One of the organizers of Thursday’s demonstration said they had asked only women to attend because they feared infiltration by plainclothes male agents.

Across the street from the protesters, beside police officers, men stood making lewd gestures and yelling profanities. Others chanted in favor of President Abdel Fattah al-Sisi.