Egypt's Interior Ministry said the raids, conducted at dawn Saturday, targeted three suspected hideouts of terrorists who were planning hostile acts during the Christmas holidays, according to the state-run Al-Ahram online newspaper.Ammunition, firearms and improvised explosive devices were recovered in significant numbers, Al-Ahram said, citing a ministry statement.The raids were ordered "as a continuation of the ministry's efforts in chasing terrorist elements involved in the implementation of hostile operations seeking to destabilize the country's security," the statement said. "Information was available to the national security sector about the preparation and planning of a series of terrorist attacks targeting state institutions, especially economy, tourism industry, armed forces, police and Christian houses of worship." Three Vietnamese tourists and an Egyptian tour guide were killed and at least 11 people were injured in the attack Friday in a central tourist area of Giza, near Cairo, where the pyramids are located.The improvised explosive device was hidden near a wall on El-Maryoutiya Street in Giza's Haram district and went off as the bus went by, authorities said. No one has claimed responsibility.Vietnam's Foreign Minister and Deputy Prime Minister, Pham Binh Minh, said he was "deeply saddened" by the attack.Egyptian Foreign Ministry spokesman Ahmed Hafez called the bombing "a despicable, cowardly terrorist act" in a statement on Twitter. "We extend our sincere condolences to the victims' families in Vietnam and Egypt. We will continue to move towards a new year of determination to root out terrorism," he said.The US State Department also condemned the attack. "We stand with all Egyptians in the fight against terrorism and support the Egyptian government in bringing the perpetrators of this attack to justice," it said.
CNN's Jennifer Deaton, Mohammed Tawfeeq, Hossam Ahmed and Hamdi Alkhshali contributed to this report.