A policeman and a civilian were also wounded yesterday evening when assailants threw the bomb from a nearby bridge onto the kiosk, located on a main square of the Egyptian capital, the officials said.
Militants have stepped up their attacks against security forces since the army ousted Islamist president Mohamed Morsi in July and the military-installed authorities launched a deadly crackdown on his supporters.
More than 1,400 Morsi supporters have been killed in the crackdown, according to Amnesty International, and thousands others have been jailed.
The attacks, many of them occurring in broad daylight, have been carried out in the restive northern Sinai, where an Islamist militancy is growing rapidly, as well as in the Nile Delta and in Cairo.
On Thursday, a little-known jihadist group, Ajnad Misr, claimed some of the latest attacks and vowed new ones.
The deadliest attacks have been claimed by Sinai-based Ansar Beit al-Maqdis, a jihadist group inspired by Al-Qaeda.