0350 GMT May 25, 2019
Thirty alleged "terrorists" were killed in separate raids in Giza governorate, home to Egypt's famed pyramids and the scene of Friday's deadly bombing, while 10 others were killed in the restive North Sinai, the Interior Ministry said without directly linking them to the attack, AFP reported.
It said authorities had received information the suspects were preparing a spate of attacks "targeting state institutions, particularly economic ones, as well as tourism, armed forces, police and Christian places of worship."
A security source said the raids took place early Saturday morning, hours after Friday evening's roadside bombing which officials said hit a tour bus in the al-Haram district near the Giza pyramids killing the three Vietnamese holidaymakers and their Egyptian guide.
Eleven other tourists from Vietnam and an Egyptian bus driver were wounded, the public prosecutor's office said.
Saigon Tourist, the company that organized the trip, said the tourists were "on their way to a restaurant for dinner" when the bomb exploded.
Company officials were heading to Cairo on Saturday and plans were made to allow some relatives of the victims to also fly to Egypt.
Vietnam's Foreign Ministry spokeswoman Le Thi Thu Hang thanked Egyptians who were caring for the survivors.
"Vietnam is very angry and strongly condemns the terrorist act that killed and injured many innocent Vietnamese and has asked Egypt to soon open an investigation, chase and give harsh punishment to those who carried out these terrorist act," she said in a statement.
Iran also condemned the attack, calling a “hideous and despicable” act against innocent people.
There was no immediate claim of responsibility for the bombing, the first attack to target tourists since 2017.
Friday's attack was the latest blow to Egypt's vital tourism industry, which has been reeling from turmoil set off by the 2011 uprising that forced former president Hosni Mubarak from power.
While tourism has picked up since 2011, the 8.2 million people who visited Egypt in 2017 are still a far cry from the 14.7 million who visited in the year before the uprising.
Egypt has been seeking to lure tourists back by touting new archaeological discoveries and bolstering security around archaeological sites and in airports.
It is also planning to open a major museum near the Giza pyramids – the only surviving structures of the seven wonders of the ancient world.
In July 2017, two German tourists were stabbed to death by a terrorist at the Red Sea resort of Hurghada.
In October 2015, a bomb claimed by a local affiliate of the Daesh terror group killed 224 people on board a passenger jet carrying Russian tourists home from the Sinai Peninsula.