At least five people were killed and almost 100 more wounded after explosions rocked Cairo on Friday morning, Egypt's Ministry of Health said.
Fierce clashes later broke out between thousands of supporters of deposed Islamist President Mohammed Morsi and Egyptian security forces, who fired teargas at the Molotov cocktail-hurling demonstrators.
Shortly after sunrise, a vehicle exploded as it tried to get into police headquarters in the Egyptian capital, killing four and wounding 76, officials told NBC News.
"Traitors and dogs," onlookers yelled in an apparent reference to the assailants, according to Reuters. Witnesses also told local media that there was damage to both the police headquarters building and the 19th-century Museum of Islamic Art, which was recently renovated in a multi-million dollar project.
State television quoted witnesses as saying that gunmen opened fire on buildings after the blast.
With smoke still rising over the city center from the blast, a second explosion next to a subway station again shook Cairo. A Ministry of Health spokesperson said one person died and another four were wounded in the second explosion.
Egyptian TV later reported a third explosion from an improvised explosive device next to a police station near the Pyramids district of Giza on the outskirts of Cairo, but NBC News was not able to immediately verify the report. There were no immediate reports of casualties.
Almost 2,000 Morsi supporters later gathered on the road leading to Giza, some burning tires and others throwing petrol bombs at security forces, who responded by firing teargas in a bid to disperse the crowds.
Henry Austin reported from London.
— Reuters and The Associated Press contributed to this report.