(Ahlul Bayt News Agency) - At least one person was arrested, but there were no reports of casualties.
Police accused demonstrators, who were demanding reforms in the job market, job-security and an end to corruption, of anarchism. In Saudi Arabia, protests and political gatherings of any kind are prohibited.
Saudi activists said by banning streets protests, the government is suppressing democracy, freedom of thought, and speech.
The rare Riyadh protest came as British Prime Minister David Cameron is in the country for talks with the ruling Al Saud family.
Meanwhile, hundreds of anti-government demonstrators have taken to the streets in the oil-rich Eastern Province to protest the killing of a young protester by Saudi forces.
The 22-year-old Esam Mohamed Abu Abdellah was killed on Thursday after Saudi forces opened fire on anti-regime protesters in the eastern city of Awamiyah.