Petrol bombs were thrown during the night by unknown attackers at a parking lot of a Saudi Arabian court in the kingdom's unrest-hit Shiite-populated east, an official and witnesses said on Sunday.
They said the bombs were thrown in the parking lot outside the compound of the court in Qatif district, setting the plastic shades that covered the area on fire.
"The shades of the parking lot outside the court caught fire," said a civil defence official in Eastern Province as videos posted on social networking websites showed the blaze.
Attacks on Saudi government facilities in Qatif have increased after the deaths of two Shiite protesters during clashes with the police there last week.
On Friday, the interior ministry announced that a gunman was killed during an attack on a police station and four Saudi policemen were wounded in a separate assault on their patrols in the same region.
Qatif witnessed several protests triggered in February 2011 after an outbreak of violence between Shiite pilgrims and religious police in the holy city of Medina.
The sporadic protests escalated after the kingdom led a force of Gulf troops into neighbouring Bahrain to help crush a month-long Shiite-led uprising last year against that country's Sunni monarchy.
Last week, tensions intensified after authorities arrested prominent Shiite cleric Nimr al-Nimr, described by the kingdom as an "instigator of sedition."
Saudi Arabia's estimated two million Shiites, who frequently complain of marginalisation, live mostly in the east, where the vast majority of the OPEC kingpin's huge oil reserves lie.
Some 37 Shiite clerics released a joint statement on Friday in which they urged youths to "steer away from violence" and not to "respond to some who try to provoke you and lure you to violence to mark your movement as terrorist."
In May, Amnesty International said seven people had been killed and a number of others injured in clashes between the authorities and protesters in the Shiite-populated region since November.