A powerful blast tore through a police headquarters in Cairo in the deadliest bombing yet in a months-long wave of violence.
So far 13 people are confirmed dead with more than 100 people wounded and many still buried under the rubble.
Officials have pinned the blame on the Muslim Brotherhood, which has been leading a campaign of protests since the July ousting of Islamist President Mohammed Morsi.
The Brotherhood in turn accused the government of trying to scapegoat it to justify intensifying a crackdown.
As well as causing loss of life, the blast brought down an entire section and side wall of the five-floor building.
Dozens of parked cars were incinerated, and several nearby buildings were damaged, including a bank and theatre.
Security sources believe that a pick-up truck carrying a large amount of explosives caused the blast.
No traces of the bomb or vehicle have been found, and investigators believe that it could have been detonated by remote control
At the funeral for the 12 policeman and one civilian killed, hundreds massed at the site of the bombing in the city of Mansoura.
They chanted: ‘The people want to execute the Brotherhood,’ They raised posters reading ‘no to terrorist groups’ and pictures of military chief General Abdel-Fattah el-Sissi, who removed Morsi and is the country’s most powerful figure.
Violence in Egypt has escalated since the government launched a crackdown on the Muslim Brotherhood.
Most attacks have been centered in the Sinai Peninsula, where multiple militant groups operate, but the insurgency has been spreading to the heavily populated Delta and the capital, Cairo.
The military-backed interim government has sought to portray the Brotherhood as largely responsible for violence, though authorities have presented no evidence.
A government panel was meeting Tuesday and Wednesday to discuss declaring the group officially as a ‘terrorist organisation.’
Tuesday’s attack on the security headquarters in Mansoura, was the first major bombing in the Nile Delta.
The same building had been targeted in July, when an explosive planted outside killed a policeman and wounded another.