At least 16 people were injured in the blast on the road outside the new Grand Egyptian Museum in Cairo on Sunday.
The bus was carrying 28 South African tourists from the airport to the pyramids. Several Egyptians in nearby vehicles were also injured by broken glass.
There was no immediate claim of responsibility for the attack but Egyptian security forces have been waging a counter-insurgency campaign against Islamist militants in the north of the Sinai Peninsula.
Mohamed el-Mandouh, who witnessed the blast, said he heard a “very loud explosion” while sitting in traffic nearby.
Images showing a damaged bus with its windows blown out and what looked to be injured tourists, some covered in blood, have been circulated on social media.
South Africa’s foreign ministry said in a statement that three of its citizens were injured and will remain in hospital. The other 25 passengers will return home on Monday morning, it claimed.
The blast happed around 50 metres from the outer fence of the new museum, and more than 400 metres from the main building, according to the Antiquities Ministry.
Egypt’s tourist industry has been recovering in recent years after visitor numbers dropped in the wake of a 2011 uprising and the 2015 bombing of a Russian passenger jet.
The museum, which will display some of the country’s top antiquities on a site adjoining the world-famous Giza pyramids, is due to open next year.
In December, three Vietnamese tourists and an Egyptian guide were killed and at least 10 others injured when a roadside bomb hit their tour bus less than 2.5 miles from the Giza pyramids.
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