A suicide car bomber destroyed a Saudi security forces building in the capital today, killing a senior officer and at least nine other people.
Medical and security sources in Riyadh said more than 70 were wounded in what an official said was the sixth attempt at such a "terrorist attack" in a week. Five others were foiled.
The bomber tried to crash his vehicle into the compound in downtown Riyadh at noon (Irish time) and set off a huge blast 30 metres from the building when guards tried to stop him, the Saudi Interior Ministry said in a statement.
Coinciding with a visit by a top US official to a city where 50 people died last year in suicide attacks on foreigners, the bomb tore the front off the six-storey administrative block.
There were no reports of foreign deaths in the latest bombing. The kingdom, a key US ally and the world's largest oil exporter, is battling a tide of Islamist militancy linked to Saudi-born Osama bin Laden's al Qaeda network.
Last week, Washington ordered non-essential diplomats out and said other Americans should leave, citing fresh signals of possible attacks on Western interests.
The US embassy closed early after today's bombing, a US official said.