A recently emerged armed group claimed responsibility for a bomb attack in Cairo that killed six policemen.
The Hasm movement, which has said it was responsible for several attacks in Egypt in recent months, made the announcement in an internet posting on Friday. Three other officers were wounded.
The Hasm movement said it targeted a police checkpoint in Haram Street, close to the famous Giza Pyramids with an explosive device.
"The explosion was very loud. We thought it was an earthquake. The glass of windows near the area broke because of the severity of the blast," a witness told state TV.
Conflicting reports surrounded the attack.
A statement on the official Facebook page of the Egyptian Interior Ministry confirmed a crude explosive device went off near the checkpoint. But state TV reported the blast was caused by a car bomb.
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The bombing, close to a government building in a middle-class neighbourhood of Cairo, was the latest in a series of similar attacks across Egypt.
Security forces killed three gunmen on Tuesday in a raid on a hideout in southern Egypt used by what they described as an armed wing of the Muslim Brotherhood, which claimed responsibility in September for an assassination attempt on a senior prosecutor.
The Hasam movement, had previously claimed several attacks in or near Cairo, including the assassination of a police officer.
An Egyptian general was killed by armed fighters on November 4 near his home in North Sinai, in an attack that ISIL claimed responsibility for. He was the second military officer of his rank to be shot dead in as many weeks.
Hundreds of soldiers and police have been killed in attacks by several armed groups mainly concentrated in the Sinai peninsula since the 2013 military coup that ousted Mohamed Morsi, the country's first democratically elected president.
A new group calling itself Liwa al-Thawra, or the Revolution Brigade, claimed responsibility for an attack on October 22 in Cairo.
The violence has dented the recovery of tourism after the 2011 uprising drove away tourists, a major source of hard currency.
Import-dependent Egypt is facing a shortage of foreign exchange that has stifled business activity and hit confidence in the economy.
Source: Al Jazeera and news agencies