At least six people have been killed and up to 80 others injured after a string of bombings targeted the police and government buildings in Egypt.
The first explosion hit the police headquarters in Cairo before Friday prayers and badly damaged the nearby Islamic Art Museum.
A second explosion struck a few hours later near a metro station in the Dokki area of Giza, a district of Cairo. It was followed by a third blast near a police station in Al-Ahram area of Giza.
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The fourth explosion occurred in front of a cinema, also in Giza.
Ansar Beit al-Maqdis, an al-Qaeda-inspired group led by bedouin fighters in the Sinai Peninsula, said late on Friday that it carried out the attacks earlier in the day in the Egyptian capital.
The bombings came on a day street clashes across Egypt between Islamist supporters of deposed President Mohamed Morsi and backers of the military killed 14 people.
They struck a day before police were to deploy across Cairo for the third anniversary of the Arab Spring uprising that toppled long-time President Hosni Mubarak.
Catherine Ashton, EU foreign policy chief, who had tried unsuccessfully to mediate between Morsi's supporters and the interim government in August, condemned the bombings.
"Violence will not bring Egypt any closer to the people's desire for a democratic country," she said.
The pro-Morsi National Pro-Legitimacy Alliance also condemned the bombings but said it would go ahead with its "peaceful struggle against [the] coup".
Surveillance camera footage
Security cameras captured the attack on the Cairo police headquarters. The blast occurred after a white pick-up vehicle pulled up outside the building, and the driver emerged to get into a waiting car.
Soon after, two police officers can be seen inspecting the vehicle and walking into the building, moments before the explosion covered the screen in a flash of smoke and flames.
Police confirmed the authenticity of the footage aired by Egyptian media, adding that the guards in the video had gone inside to raise the alarm.
The blast, which killed four people and wounded dozens badly, damaged the facade of the security directorate and left a crater in the ground. It brought down ceilings and damaged exhibits inside the Museum of Islamic Art.
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Riot police pushed back hundreds of onlookers, some of whom chanted slogans against Morsi's Muslim Brotherhood.
Others carried Egyptian flags and posters of General Abdel Fattah el-Sisi, the army chief who overthrew Morsi.
Angry residents - some chanting for the "execution" of Muslim Brotherhood members - joined police in clashes with the group's supporters holding their daily street protests against the government.
Smoke rose over Cairo from fires, and fighting around the country left 14 more people dead.
The office of Adly Mansour, the interim president, pledged to "avenge our martyrs".
"Whoever planned, participated, financed, or incited [the attack] will be punished with the worst form of punishment," it said.
Islamist supporters of Morsi have called for mass protests against the new regime.
The Muslim Brotherhood was blacklisted as a terrorist group after 15 people were killed when a suicide bomber blew up a vehicle at a police headquarters north of Cairo in December.
More than 1,000 people, mostly Islamists, have been killed in violence since Morsi's overthrow last year.
Thousands more have been jailed, including Morsi and other Muslim Brotherhood leaders.
Ansar Beit al-Maqdis, claiming responsibility for Friday's bombings, said they were aimed to avenge the killings of Morsi's supporters.
The group issued an online audio statement on Thursday urging police and soldiers to defect or else face new attacks.
Scores of soldiers and police have been killed in the Sinai, and fighters in the desert region have begun to expand their operations to densely populated areas along the Nile.
Masked assailants on motorbikes killed five policemen south of Cairo on Thursday.
There have also been bombings in Cairo, including a failed assassination attempt against the interior minister in September, just weeks after policemen killed hundreds of Morsi supporters at a protest camp.
Source: Al Jazeera and agencies