RIYADH, April 21: At least 10 people, six of them security personnel, were killed and up to 70 others injured when at least one car laden with explosives blew up a building of the Saudi General Security Services here on Wednesday.

Those killed included a colonel of the public security department, a Saudi government official said. The body of a suspected bomber had been found, a spokesman for the Saudi Ministry of Interior has been quoted as saying.

Witnesses said the front portion of the six-storey building, which is part of the security headquarters in Al Washm district, was destroyed in the attack. There was confusion about the number of cars involved in the attack and some reports suggested the two cars had exploded near the building.

According to residents, the explosion took place at around 1425 hours local time (1125 hours GMT), at a protective barrier outside the building, shattering windows of several adjoining buildings in the area.

The area was cordoned off by police after the blast and ambulances were seen rushing towards the place. A Riyadh resident said a large number of ambulances could still be seen, a couple of hours after the blast, taking victims to hospitals.

Fires raged long after the explosion which left a deep crater and the street covered in debris. Dozens of twisted and blackened cars still smouldered and glass shards and concrete blocks lay thickly on the tarmac.

In the immediate aftermath of the explosion, smoke enveloped the skyline of the central Al Murabba and Al Washm quarters, an area of Riyadh which also houses state television and the information ministry.

The Saudi television showed the entire government building wrecked by the explosion. "A huge explosion took place in a building and a fire broke out," it said. The blast has taken place after security forces announced confiscation of at least five explosive-laden cars over the last few days.

News agencies quoted an interior ministry spokesman as saying that the blast was a terrorist attack. According to reports, this was the sixth attempt to mount such a "terrorist attack" in a week. Five earlier attempts had been foiled. At least five policemen died last week in Riyadh in clashes with extremists.

AFP ADDS: The interior ministry said four people, including two security men, were killed and 148 injured in the blast. "Up until this statement was written, there were four deaths. Two security men were martyred, in addition to a civilian employee, and an 11-year-old Syrian girl," said a ministry statement read on state television.