The tanker crashed into the National Guard Bridge in Riyadh and exploded, damaging nearby houses and vehicles, state news agency SPA reported.
Director General of Civil Defense Saad bin Abdullah al-Tuwaijri blamed the crash on the driver.
Some 10,000 people gathered at the scene, Tuwaijri said, despite warnings from police to stay away because of possible secondary explosions.
Ali al-Qahtani, commander of Ring Roads and Secret Police Traffic in Riyadh, said the road was closed in both directions around the scene and would not reopen before Friday.
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