The Egyptian militant group Ajnad Misr claimed responsibility on Saturday for a blast that killed one police officer in Cairo.
The bomb exploded in Cairo's Lebanon Square on Friday night, killing the officer and wounding another.
Ajnad Misr, or Soldiers of Egypt, said in a statement on an Islamist website that its militants had monitored a police checkpoint in the square before detonating the bomb.
The group formally announced itself in January saying it would target "criminal elements" in the military-backed government.
It has claimed at least six attacks since then, including explosions outside Cairo University which killed a police brigadier-general and one other person earlier this month.