Three small bombs exploded minutes apart in three Cairo metro stations during early morning rush hour on Wednesday, injuring at least five people, according to Al-Ahram's Arabic news website, with a fourth blast injuring a sixth passenger reported later by the same source.
The first three metro blasts were followed an hour later by two other bombs near a courthouse in Heliopolis, eyewitnesses and Al-Ahram's Arabic news website have reported.
The metro blasts injured three people at the Shubra station, medics and security sources said, while state TV has reported one injury at the Ghamra station. A senior ambulance official, Mohamed Sultan, said the fifth injury occurred at the Hadyek Al-Quba station, and the sixth injury, reported by Al-Ahram's Arabic new website, took place at the Ezbet Al-Nakhl station.
The Ministry of Interior said in a statement on Facebook, however, that only two blasts had taken place: one in the Shubra station and the other in the Ghamra station.
The first blast, which took place in the northern Shubra station, interior ministry spokesman Abdel-Fattah Othman said, was caused by an improvised bomb, while the second resulted of a sonic explosive placed in a rubbish bin at Ghamra station, on a different metro line.
A person who appeared to be carrying a home-made bomb was wounded at the Shubra station, the ministry statement went on, adding that no one was injured in the Ghamra station blast.
The ministry spokesman also said that one of the injured in the metro station blasts was a suspect.
An official at the metro company told state news agency MENA that metro services are operating normally.
The two improvised bombs in the upscale Heliopolis district were placed underneath two cars outside a courthouse, Al-Ahram said, adding that the blasts damaged the cars but left no injuries.
A third home-made explosive device planted in the vicinity was defused, according to Al-Ahram.
Security sources continue to comb the sites of the blasts for further explosives, the interior ministry said.
Wednesday's Cairo explosions come after weeks of relative calm that followed a previous spate of frequent violence and palpable volatility.
Islamist militants had stepped up attacks in Egypt since the army's ouster of Islamist president Mohamed Morsi last July amid massive protests against his rule and an ensuing deadly crackdown on his supporters.
Former army chief Abdel-Fattah El-Sisi, who led Morsi's ouster, was sworn in as Egypt's new president earlier in June after he won a lopsided election victory.
Most of the attacks, mainly targeting security forces, had been initially focused in the sparsely populated Sinai Peninsula but eventually spilled over into other cities, including Cairo and the Nile Delta.
According to a government tally, the violence has killed at least 500, mostly policemen and troops.
Ansar Beit Al-Maqdis (Supporters of Jerusalem), an Al-Qaeda-inspired group based in Sinai, has claimed some of the deadliest attacks on security forces, as well as a failed assassination attempt on the interior minister in September.
It says the violence is in retaliation for the state clampdown on Islamists.