"At least eight people were killed," a security official told reporters on Wednesday. He said: "Eighty three people were taken for treatment at the Shmaisa Hospital in Riyadh and 30 more wounded were transferred to King Faisal Specialist Hospital," also in the capital.
"An 11-year-old girl and an unidentified person succumbed to their wounds," the official said.
Security personnel killed
Earlier, a police official had said at least six Saudi security personnel were killed after at least one car bomb demolished a building in Riyadh.
"Six members of the security forces were killed. They include a colonel from the public security department and the department's financial director," the official told reporters.
The blast clogged with smoke the central al-Muraba and al-Washm quarters of Riyadh which also houses the state television and the information ministry.
Witnesses said a human bomber drove the explosives-laden car into the building used by security services. Local residents said the front of a building had been completely blown off.
Hanan Battisha, an Egyptian housewife, heard a "big blast" and rushed down the stairs with her two children, aged 14 and 11.
Witnesses say the blast was
caused by a human bomber
"We heard wails and cries, then saw our neighbours running down the stairs," she said. By the time they reached the ground floor, "the gate was damaged, windows started shattering, and glass fell all over us."
"The fronts of the buildings around us were damaged, the air conditioners mangled and there was smoke everywhere," she said.
Islamist fighters who see the country as a US ally have stepped up attacks on Saudi Arabia's security services.
Five policemen died last week and army units defused three car bombs in the capital.
Saudi-born Usama bin Ladin has also called for the removal of the country's monarch and his al-Qaida network is accused of killing nearly 50 people in the kingdom last year.
Last Thursday, the US ordered its non-essential diplomats out of the Gulf Arab state and told all Americans that they should leave, citing fresh signals of possible attacks on US and Western interests.
Human bombings at foreign residential compounds in Riyadh
killed 50 people last year, including nine Americans.