The improvised explosive device was placed near a wall along Mariyutiya Street in the Haram district near the Giza pyramids, the interior ministry's statement said.
The bombing took place in the Giza region near Cairo, where the pyramids are located.
Madbouly explained that, however, the bus carrying the Vietnamese tourists deviated from the pre-determined, secured route without apriori notifying security officials.
The PM said that the number of injured still under treatment stands at 10 with two in critical condition.
Three of the tourists were killed along with the tour guide, an Egyptian citizen, Attorney General Nabil Ahmed Sadeq said in a statement.
"We have to know that it's possible that it would be repeated in the future".
Winter weather advisory for Cascades through Thursday
The sloppy weather will continue into the afternoon, with light snow in the far north and rain elsewhere. Around the Red River Valley, Speicher said there was about 4-8 inches of snow that gathered overnight.
Kyle Kuzma takes blame for Lakers’ loss to Kings
He has appeared in all 34 games this season and did not miss a game last season with the Cleveland Cavaliers. James was injured in the third quarter of the team's Christmas Day win over the Golden State Warriors.
Post-holiday, partial government shutdown to gain impact
The House and Senate briefly gaveled into session on Christmas Eve before quickly closing again with no further action. The federal budget impasse is over President Donald Trump's push for money to build a border wall.
Egypt's army and police launched a major campaign against militant groups in February, targeting the Sinai Peninsula as well as southern areas and the border with Libya.
Two German tourists were stabbed to death at a hotel in the popular Red Sea resort of Hurghada a year ago.
"It was bad - people screaming", she said.
Madbouly said the Egyptian authorities have been in contact with the embassy of Vietnam.
In 2015, ISIS claimed responsibility for a blast that downed a Russian airliner and killed all 224 people aboard shortly after it took off from the Egyptian holiday resort of Sharm El Sheikh. The official statistics agency says tourists arrivals in Egypt in 2017 reached 8.2 million, up from 5.3 million the year before.