CAIRO — A bus full of Vietnamese tourists was rocked by a roadside bomb near the famed Giza Pyramids on Friday, killing at least four people and wounding 10 more, officials said.

The primitive explosive had been stashed by a wall in the Mariotiyah area near the pyramids, the Interior Ministry said. The dead included three Vietnamese tourists and an Egyptian tour guide.

Prime Minister Mostafa Madbouly told reporters that the bus had left its designated route without notifying authorities. Images from the scene of the attack showed a small white bus covered in soot with its windows shattered and blown out.

No militant group immediately claimed responsibility for the attack, but Egypt has been fighting an Islamic State affiliate in Sinai since 2013.