A car belonging to a senior officer in the Saudi security forces has exploded in Riyadh, but no-one was hurt.
There has been a wave of attacks in Riyadh
The blast happened on Monday evening shortly after the officer parked the car outside his home in the al-Salam district of the capital.
Witnesses said a car sped by the parked vehicle and a device was thrown at it - but this has not been confirmed.
The explosion comes at a time when the Saudi authorities are conducting a campaign against Islamic militants.
"It was a small blast and the car was not stuffed with explosives but we are investigating the incident," a Saudi interior ministry official told Reuters.
Earlier this month, a militant group called the al-Haramain (the two mosques) Brigades said in a statement on an Islamist website that it had tried to kill a senior interior ministry official.
In November, an attack on a residential compound Riyadh in November left 18 dead as well as 120 wounded, many of them children.
Two of the bombers involved in the attack were identified by police as Saudi nationals.
Suicide attacks on Western diplomatic compounds in May left 34 dead, including the nine bombers.
The UK Government warned this week that terrorists could be in the final stages of planning an attack in Saudi Arabia.