Correction April 5, 2015: This article originally stated that three people have been killed in a blast on a bridge in the Egyptian capital, according to state media.

One policeman has been killed in a blast on a bridge in the Egyptian capital, according to a witness and police.

Sunday's explosion went off on the 15 May Bridge that runs over the Zamalek district and links the governorates of Cairo and Giza.

Dozens of people gathered at the scene, some yelling in outrage, others in fear or grief. 

Sharif Kouddous, a local journalist on the scene, told Al Jazeera that traffic had been stopped on the bridge as police were collecting shrapnel and assessing damage. Several cars had their windows blown out.

"All of a sudden a bomb exploded and there was lots of smoke,'' the AP news agency quoted eyewitness Ahmed Hussein as saying.

"The soldier in the kiosk was killed. His body was torn apart.''

The bomb was reportedly placed under the police kiosk in question.

A correspondent with the AFP news agency said there was a pool of blood next to the checkpoint.

Attacks mainly targeting Egyptian security forces have spiked since the 2013 military overthrow of President Mohammed Morsi following massive protests against his divisive rule.

Morsi's Muslim Brotherhood, the strongest political movement before his overthrow, has been designated a terrorist group although it denies it is violent.

The bombings in Cairo have mainly consisted of small, homemade explosives that cause few casualties. They have hit civilian areas, including Cairo's leafy Maadi suburb, where many foreigners live, but such incidents are extremely rare in Zamalek.

Source: Al Jazeera and agencies