The blast was said to have happened in the south of the city in the Giza district, which is home to the world-famous pyramids. It is unknown who or how many people were on the bus. Russian state television channel Russia Today has tweeted: “Several people have been reported dead as well as wounded.”
Egypt’s interior ministry confirmed the bus had been carrying a party of tourists from Vietnam.
A statement issued shortly after the blast said two Vietnamese tourists had been killed and 12 others had been injured.
Ten of the people were also Vietnamese tourists, with the other two Egyptian nationals, including the bus driver, the ministry added.
The bus was hit by an explosion from an improvised device hidden near a wall on Marioutiya street at around 1815 (1615 GMT).
Police are investigating, the statement said.
Pictures from the scene showed the badly damaged bus, with windows blown out by the force of the blast.
So far, no terror group has claimed responsibility for the attack.
The area was evacuated by security forces after the explosion, with casualties taken to hospital.
The pyramids are one of the world’s major tourist attractions, attracting almost 15 million visitors annually.
In 2015, ISIS claimed responsibility for an explosion which destroyed a Russian commercial airliner shortly after it took off from the Egyptian holiday resort of Sharm El Sheikh – but this is the first terror attack to target foreign tourists in almost two years.
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