The Egyptian authorities say an explosion in Cairo's historic centre was caused by a male pedestrian throwing a bomb in the area popular with tourists.
Health and police officials said the blast killed up to four people, among them a US citizen and a French citizen, and wounded 18 others.
Police sources earlier said a man riding a motorcycle had thrown the bomb.
The bombing is the latest in a series of attacks on tourists in Egypt, which thousands of foreign nationals visit each year to see its ancient treasures and pyramids.
