Security forces stand near a tourist bus after a roadside bomb in an area near the Giza Pyramids in Cairo, Egypt, Dec 28, 2018.  (NARIMAN EL-MOFTY / AP)

CAIRO - Egyptian security forces have killed 40 suspected militants in three separate incidents in North Sinai and Giza, the ministry of interior said on Saturday, a day after a deadly bombing on a Vietnamese tourist bus in Giza killed four people.

Three Vietnamese tourists and an Egyptian guide were killed and at least 10 others injured when a roadside bomb blast hit their tour bus on Friday less than 4 kilometers from Egypt's world-famous Giza pyramids, authorities said. 

The bombing is the first deadly attack against foreign tourists in Egypt for over a year and comes as the tourism sector, a vital source of foreign currency revenue, recovers from a sharp drop in visitor numbers since the country's 2011 uprising. 

No immediate claim of responsibility was reported. 

Islamist extremists, including militants linked to Islamic State, are active in Egypt and have targeted foreign visitors in the past. 

At least nine Vietnamese tourists were injured, as well as the Egyptian driver, according to official statements. 

Egyptian authorities did not say whether the suspected militants killed on Saturday were connected to Friday's attack, but said its forces killed 30 people during raids on their hideouts in Giza where it said "terrorist elements" were planning a series of attacks targeting state institutions and the tourism industry.

Security forces also killed 10 suspected militants in North Sinai, where the country is fighting an insurgency led by Islamic State.

State news agency MENA said that the suspects were killed in a gun battle. 

WRONG ROUTE?

Vietnam's foreign ministry confirmed on Saturday that three of its citizens had been killed in the blast, and that it was working closely with Egypt's interior ministry to provide assistance to the injured and to their families.

In this photo released by Vietnam Embassy in Cairo, Vietnamese ambassador visits an injured Vietnamese tourist at a hospital in Cairo, Egypt, Dec 28, 2018. (VIETNAM EMBASSY IN CAIRO VIA AP)

Egyptian Prime Minister Mostafa Madbouly, told media from Al Haram hospital that the bus had taken an unexpected route. 

"The bus deviated from the route secured by the security forces," Madbouly told Extra News channel, an assertion also made by the owner of the company that organized the bus tour. 

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"We have been in contact with the embassy of Vietnam to contain the impact of the incident, and what is important now is to take care of the injured," the prime minister said. 

The bus driver later told local media he had not deviated from the route. 

The damaged tourist bus after a roadside bomb in an area near the Giza Pyramids in Cairo, Egypt, Dec 28, 2018. (NARIMAN EL-MOFTY / AP)

Madbouly urged the international community to unite in the face of terrorism, noting that such incidents cannot stop the Egyptians' development.

We were going to the sound and light show and then suddenly we heard a bomb. It was terrible, people screaming

 Lan Le, tourist 

The tourists were heading to a sound and light show at the pyramids, which they had visited earlier in the day, said Lan Le, 41, who was also aboard the bus but unhurt. 

"We were going to the sound and light show and then suddenly we heard a bomb. It was terrible, people screaming," she told Reuters, speaking at Al Haram hospital, where the injured were taken. "I don't remember anything after." 

Egypt's interior ministry said the bus was hit by an explosion from an improvised device hidden near a wall at around 1815 local time (1615 GMT). 

About two hours later the vehicle could be seen behind a police cordon with one of its sides badly damaged and the windows blown out, a Reuters reporter said. 

Dozens of police, military and firefighters were at the site, on a narrow sidestreet close to the ring road, where traffic was moving normally. 

Security forces stand near a tourist bus after a roadside bomb in an area near the Giza Pyramids in Cairo, Egypt, Dec 28, 2018. (NARIMAN EL-MOFTY / AP)

Shortly afterward, workers brought a pick-up truck to tow the bus away. 

An investigator at the scene said the device had likely been planted near the wall. 

The interior ministry confirmed the death of two of the tourists, and the state prosecutor's office later said a third had died. In total, 14 Vietnamese tourists had been traveling on the bus, it said. 

WIDE CRITICISM

Friday’s deadly attack was widely criticized by the Egyptian official and foreign countries. 

An investigator at the scene said the device had likely been planted near the wall

Head of the European Union (EU) Delegation to Egypt Ivan Surkos strongly deplored the attack. 

The Kuwaiti Emir Sheikh Sabah Al-Ahmad Al-Jaber Al-Sabah sent a cable to Egyptian President Abdel-Fattah al-Sisi, expressing Kuwait's condemnation of the explosion, Egypt's official MENA news agency reported. 

The Bahraini Ministry of Foreign Affairs has also condemned the terror attack, affirming the kingdom's full solidarity with Egypt in its efforts to combat violence and terrorism of all forms, and vowed support to its efforts to enhance security and peace. 

The attack came days before Egyptians celebrate New Year and Christmas, which is marked by Coptic Egyptians on Jan 7. 

Copts make up 10 percent of Egypt's 100 million population. 

This week, Egypt's armed forces, in coordination with the Ministry of Interior, intensified measures to secure Christmas and New Year's celebrations nationwide. 

In this file photo taken on Oct 2, 2018, horse riders gallop near the Giza pyramids, on the southwestern outskirts of the Egyptian capital Cairo. (JOSEPH EID / AFP)

Egypt has been fighting against a wave of terror activities since the military toppled former Islamist President Mohamed Morsi in July 2013 in response to mass protests against his one-year rule and his currently blacklisted Muslim Brotherhood group. 

Terror attacks in Egypt had mainly targeted police and military men in North Sinai before spreading nationwide and targeting the Coptic Christian minority as well, leaving dozens of them dead. 

Terrorists attacked two Coptic churches in the cities of Tanta and Alexandria in early April last year, killing a total of 47 people and wounding 106 others. 

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Most of the attacks were claimed by a Sinai-based group loyal to the Islamic State extremist group.

Those events and the bombing of a Russian airliner shortly after it took off from Sharm el Sheikh in 2015 caused tourist numbers to plunge. 

The last deadly attack on foreign tourists in Egypt was in July 2017, when two Germans were stabbed to death in the Red Sea resort of Hurghada.