Egypt's Interior Minister Mohamed Ibrahim survived an assassination attempt when a bomb detonated early on Thursday near his convoy in northeast Cairo, officials told Ahram Online.

Earlier reports said the blast resulted from a car bomb, but state TV said that the bomb was thrown by unknown assailants from a nearby building at around 10:30 am.

"Initial investigations showed a big-sized explosive devise targeted [at my] car while it was passing by," the interior minister told state-owned TV two hours after the attack, adding that the bomb seems to have been "remotely detonated."

The minister, who escaped the attack unscathed, said four vehicles among his convoy were "damaged", along with a number of civilian-owned cars.

At least twenty one, including six security officers and a child, were injured in the attack, according to Egypt's Ambulance Authority. Some shops were also damaged in the blast.

The wounded sustained severe injuries including leg amputations, Ibrahim added in his brief interview.

Initial investigations showed at least 50kg of TNT explosives or other chemicals were used in the blast, Al-Ahram Arabic news website reported.

The capital's Nasr City area has been the stronghold of a major protest camp by loyalists of Egypt's toppled Islamist president Mohamed Morsi. The interim government has accused Morsi's followers of "terrorism" and inciting violence.

The minister has sponsored a deadly raid by police to clear Islamist-led protest sites in Cairo and Giza mid-August which left hundreds dead and thousands injured, setting off days of bloody street violence. More than 100 members of security forces were killed in the crackdown and ensuing violence.

Since Morsi's overthrow by the military on 3 July after mass protests, police and security personnel have been subject to recurrent attacks by suspected Islamists incensed at his removal.

In July, at least two bombings at police stations outside Cairo were reported. The explosion in the Nile Delta's Mansoura left one dead.

Numerous police stations were also attacked across the country in the immediate aftermath of the bloody crackdown on pro-Morsi sit-ins. Video footage that went viral on social media networks showed a bloody attack on a police station in Giza's Kerdsa that left at least 9 policemen dead.

The army has also been battling an upsurge in militant activity in the Sinai Peninsula, bordering Israel and the Palestinian Gaza Strip.

At least 25 police killed were killed in an ambush in the lawless peninsula last month.

Dozens of soldiers and police have also been killed in drive-by shootings and rocket attacks in the desert province.  Egypt's army has killed around 100 militants, including foreigners, in recent operations.

During the 1990s, Egypt was rocked by recurrent bomb attacks by jihadist fighters and Islamist militants on tourist sites across the country, which severely crippled tourism and threatened security at the time.