One of those arrested was a Syrian man, Yaser Mohammed Al Barrazi, who the interior ministry said was preparing to carry out attacks.
Read: At least 13 killed in bomb attack on Saudi mosque
The other was a Filipino woman the ministry said was helping him. The bomb-making facility was inside a house in the Al Fahyaa district of Riyadh, it said.
On August 6, an explosion triggered by a suicide bomber ripped through a mosque used by Saudi police killing at least 13 people in the southern city of Abha, the Saudi interior ministry had said.
Read: 20 killed as suicide bomber strikes Shia mosque in Saudi Arabia
Further, on May 22, 20 people were killed as a suicide bomber blew himself up at a Shia mosque in eastern Saudi Arabia during Friday prayers, a hospital official had said.
Read: Four people killed in foiled militant attack on mosque in Saudi Arabia: media
Similarly, on May 29, four people were killed when a car exploded near a Shia mosque in Dammam, Saudi Arabia, but authorities had said militants failed in their bid to hit the mosque itself.
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