File Photo: Members of the Islamic State militant group.
Saudi Arabia said Friday it had foiled a bomb plot by the Islamic State group and blamed the jihadists for shooting dead two policemen in the capital earlier this month.
The authorities said three bomb-laden cars had been seized during investigations into the killings.
A Saudi man arrested at a farm north of Riyadh on suspicion of carrying out the shooting has confessed that he was following orders received from IS in Syria, the interior ministry said.
He was identified as 23-year-old Yazid bin Mohammed Abdulrahman Abu Niyan.
The authorities offered a one-million-riyal ($267,000, 246,220-euro) bounty for a second suspect, another Saudi identified as Nawaf bin Sharif Samir al-Anzi, wanted over several other criminal cases.
During their investigation the authorities seized seven cars, "three of them booby-trapped", as well as suspected bomb-making materials and tools, said the statement carried by the official Saudi Press Agency.
They also discovered machineguns, ammunition, money and several mobile telephones which revealed an exchange between the attackers and "terrorist elements in Syria", SPA said.
The two policemen were killed in an April 8 drive-by shooting in an eastern district of Riyadh.
The ministry said that Abu Niyan allegedly carried out the shooting while his partner, Anzi, drove the car and filmed the attack.
According to Abu Niyan, IS supplied them with the weapons, ammunition and money to carry out the shooting through a "third party whom they did not meet", the statement said.
- 'Fifth attack' by IS -
The shooting was the fifth attack on security forces and foreigners in Saudi Arabia orchestrated by IS, according to interior ministry spokesman General Mansour al-Turki.
The Sunni-dominated kingdom is part of a US-led coalition carrying out air strikes against IS in Syria and Iraq, where the jihadists have seized swathes of territory.
On March 29, two policemen were wounded in a similar drive-by shooting in Riyadh.
Turki told reporters that IS was also involved in that attack.
The suspected shooter was arrested while trying to flee to neighbouring Yemen, where Saudi Arabia is leading a separate air war on Iran-backed Shiite Huthi rebels.
In January, three Saudi border guards, including a local commander, were killed near the border with Iraq in a battle with IS supporters, according to Turki.
Westerners have been attacked in Saudi Arabia four times since October.
But only one of the incidents, in which a Dane was wounded in a drive-by shooting in Riyadh in November, was blamed on IS.
Authorities later arrested three suspects.
Saudi Arabia also accused IS-linked suspects of killing of seven members of the minority Shiite community in Eastern Province in November.
Attacks on Saudi security forces take place occasionally in the Shiite-populated east. However, such assaults are rare in the capital.
Friday's announcement follows an interior ministry warning this week of a possible attack against a shopping centre or oil facilities.
A ministry spokesman said there was "an alert" involving a mall or oil installations but did not provide further details.
The ministry also said that in the coming days the authorities would give details of a series of other "security incidents" that have been uncovered and foiled.
The ultra-conservative country is seeking to deter Saudi youths from joining the jihadist ranks.
Fighters from Saudi Arabia, Tunisia and Morocco make up the majority of about 12,000 foreign extremists who have travelled to Syria and Iraq, according to the London-based International Centre for the Study of Radicalisation.
Saudi Arabia witnessed a wave of deadly attacks by Al-Qaeda between 2003 and 2006, which prompted authorities to launch a crackdown on the local branch of the jihadist network founded by slain Saudi-born Osama bin Laden.