Three Vietnamese tourists and a local tour guide have been killed after a roadside bomb hit a bus near the Giza pyramids in Egypt.

Officials said 11 others were injured in the incident, the first affecting foreign tourists in Egypt in more than a year.

Prime Minister Mostafa Madbouly said the bus had deviated from its planned route without alerting security forces, although the driver denied this.

No group has yet said it was behind the blast.

Islamist militants have targeted tourists in the past.

Security is already tight in Egypt, with the tourist season at its height and the country’s main Christian minority, the Copts, preparing to celebrate Orthodox Christmas on 7 January.

Egypt’s neighbours in the region condemned the attack and the British Ambassador to Cairo, Geoffrey Adams, said the UK stood “with Egypt in the fight against terrorism”.

The bomb went off at about 18:15 (16:45 GMT) on Maryoutiya Street in Giza’s Haram district as the bus carrying 14 Vietnamese tourists was passing, according to official accounts.

Security forces rushed to the scene in response and police are investigating.

The injured were taken to the nearby Haram hospital, Reuters news agency reports.

All of the injured are Vietnamese tourists apart from the bus driver, who is Egyptian.

Tourism is a mainstay of the economy in Egypt.

It peaked in 2010, when the country saw more than 14 million visitors, but fell sharply after the turmoil of the Arab Spring the following year.

Worse was to come after militants bombed a Russian passenger jet in 2015 as it left Sharm el Sheikh killing 224 people.