A massive bomb went off in central Cairo early Friday morning, followed by two more explosions in the city, in the latest attacks targeting Egyptian security forces.

The first blast occurred in front of the Cairo police headquarters. Eyewitnesses reported gunmen on motorcycles exchanging fire with security forces after the explosion, according to Israel Radio.

State news agency MENA quoted an unnamed security official as saying the explosion was caused by a car bomb. At least five people were killed and 47 were wounded, according to the state radio.

A few hours later, Egyptian security officials said one person was killed and eight wounded in a blast targeting police vehicles near a metro station in Cairo.

They spoke on condition of anonymity because they were not authorized to brief the media.

Witnesses say drops of blood were scattered at the site of the attack, also next to famous Russian Culture Center in the Dokki district.

Soon after, a third blast targeted a police station near the pyramids, with no report of casualties.

Egypt has seen a sharp rise in attacks targeting police and the military in the aftermath of the July 3 coup that ousted Mohammed Morsi.

A Muslim Brotherhood-led coalition plans protests after Friday prayers across the country as part of their near-daily demonstrations against the July overthrow of Islamist president Morsi and the recent vote on the country’s rewritten constitution.

Shortly after the first explosion, the state TV aired footage showing several wrecked and charred floors of the high-rise security building with the pavement outside littered with shuttered glass, pieces of bricks and rocks.

An Associated Press photographer said about six police officers sat on the sidewalk outside the building and wept. Small parts of a vehicle could be seen scattered around on the road and a corpse — which officers said was a suicide bomber — lay under a blanket.

According to the report, gunfire resounded from the area immediately after the blast, but there were no other details.

About two hours later, rescue teams were still trying to extract victims trapped inside the security building, MENA said. The agency said the blast had also shattered windows and damaged the facades of a court house nearby.

The Islamic Museum in Cairo was also damaged in the first blast.

Ansar Beit al Maqdas claimed responsibility for Friday’s car bombing.

The attacks come a day before the three-year anniversary of the 18-day uprising against Morsi’s predecessor president Hosni Mubarak, which began on January 25, 2011, a date also known as Police Day.

Egyptians had expected that the day would cause tensions on the streets of Cairo. Military loyalists have called on Egyptians to mass in Cairo’s Tahrir Square and urge army chief Gen. Abdel-Fattah el-Sissi, who ousted Morsi, to run for president. El-Sissi has yet to announce his intentions.

At the same time, Morsi’s Islamist supporters have called for escalated protests to “break the coup” and ignite a new revolution.

Early Thursday, hundreds of pro-Morsi students clashed with security forces in fierce street battles in the Mediterranean city of Alexandria, leaving one protester dead, according to security officials. Brotherhood websites circulated pictures of the slain student, Amr Khalaf, with a bloody head. In one of his last Facebook postings, Khalaf identified himself as “the next martyr,” with a picture reading, “waiting my turn.”

In 2011, activists launched their anti-Mubarak protests on Police Day to denounce the widespread abuses by security agencies under his nearly 30-year rule — including torture, arbitrary arrests and corruption. The protests swelled into an all-out revolt against him, fueled by hatred of police, as well as economic woes and frustration with years of autocracy. Police forces virtually collapsed after battles with protesters.

The Associated Press contributed to this report.