Three bomb blasts outside a university campus in central Cairo on Wednesday killed a senior police officer and injured
at least five people, officials said, the latest in a series of attacks by militants that threaten to plunge Egypt into renewed violence ahead of a presidential election next month.

Two bombs exploded next to a police vehicle near Cairo University just before noon, officials said, while the third device detonated more than two hours later in the same location. It exploded just yards from a forensics team that had arrived to investigate the earlier blasts, the public prosecutor said.

The little-known extremist group Ajnad Misr, or “Soldiers of Egypt,” asserted responsibility for the blasts in a statement posted on an online jihadist forum Wednesday night. The statement said the attacks were in retaliation for the arrests of girls and women in ongoing security sweeps.

Ajnad Misr announced itself in January and later said it had launched a number of small-scale bomb attacks on security forces in the Cairo area. It is not known to have carried out any major assaults elsewhere in the country.

Security forces swiftly shut down the area after the blasts, blocking major roads leading to the university with metal barricades and barbed wire.

A plainclothes police officer on the scene said the bombs had been strategically placed around a police checkpoint — including in a nearby tree — where at least three officers were stationed. He was not authorized to speak to the news media. According to the state-run daily Al-Ahram, the bombs had been packed with nails.

The Interior Ministry said in a statement that Brig. Gen. Tarek El-Merghawy, head of the investigations unit for the West Giza district in greater Cairo, was killed in the first explosion. It was not clear whether Merghawy was specifically targeted, and conflicting reports in local media said a civilian had also been killed. Three other high-ranking officers were wounded, the Interior Ministry said.

Egyptian Prime Minister Ibrahim Mahlab called for an emergency meeting of his cabinet Wednesday, including the defense and interior ministers, to discuss the day’s violence.

Islamist militants have ramped up assaults on police and security personnel since the military ousted Islamist president Mohamed Morsi in a coup last summer.

Small militant cells and more organized jihadist groups, such as the Sinai-based Ansar Bayt al-Maqdis, have claimed car bomb attacks and assassinations in recent months, including in the capital. More than 430 police officers and army personnel have been killed in terrorist attacks since mass demonstrations against Morsi on June 30, according to government figures. Security forces­ have killed hundreds of Morsi supporters.

“What would you do if your brother or cousin was at that checkpoint and died?” an elderly man shouted outside the police barricades at the university. “They have no mercy,” he said of the attackers.

Egypt’s universities have become a flash point for political violence between police and students opposed to the military-backed government. Former defense minister Abdel Fatah al-Sissi resigned last week so he could run for the presidency. Authorities under Sissi have detained thousands of students and clashed with youths on university campuses since the fall. Scores of students have died in the battles.

“The police are responsible for this. They are not doing their jobs,” said Attiya Ahmed, a first-year business student at Cairo University. “There are continuous protests on the campuses, and I think they will just want to arrest more of us.”