CAIRO, Egypt -- Two homemade bombs placed in a government construction site on the outskirts of Cairo exploded Saturday, killing a teenage girl and her mother, officials said.

The explosion tore through a government telecommunication building under construction in 6 October district, a security official said. The 15-year-old girl's mother, who is the wife of the building guard, was wounded in the blast and died later.

The governor of Giza, which includes 6 October, told the private CBC channel that the explosion damaged a mobile communication tower, cutting off access for 800 clients.

Investigators said two bombs were placed under the three-story building and detonated with a mobile device, according to the Giza prosecutor's office.

In a separate incident, gunmen shot and killed two civilians late Friday in the town of el-Arish in the northern part of the Sinai Peninsula. A security official said the assailants opened fire outside a police officer's home as he was escorting two repairmen outside the front door. The police officer was unharmed.

All officials spoke on condition of anonymity because they were not authorized to brief reporters.

Egypt has seen a series of attacks mainly targeting security forces since the ouster of Islamist President Mohammed Morsi last July. The Foreign Ministry says nearly 250 police have been killed in attacks since security forces dispersed a mass sit-in by Morsi supporters last August.

On Wednesday, four small explosions went off in subway stations and outside a court building in Cairo, wounding three people and marking the first attacks since the election of President Abdel-Fattah el-Sissi, the former army chief who led last year's ouster of Morsi.

Also on Saturday, a judicial disciplinary council forced former top prosecutor Talaat Abdullah into retirement after accusing him of spying and installing surveillance devices in what was then his office. Morsi had appointed Abdullah in November 2012 during the height of a prolonged standoff with the judiciary, which protested the move, saying only it had the right to fill the post.

The current chief prosecutor, Hisham Barakat, was appointed in July, right after Morsi's ouster.