The market, the largest in the Arab world, retreated nearly 5 per cent, the most since June 2010.
Al-Rajhi Bank, the kingdom's largest publicly traded lender by market value, dropped 4.2 percent and Saudi Basic Industries Corporation, the world's largest petrochemicals maker, slumped to the lowest intraday level since October.
The Tadawul was closed on Saturday to celebrate the return of King Abdullah who had left in November for medical treatment.
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Investors were more upbeat in some stocks as shares in telecoms operator du made their first gain in nearly two weeks, rising 0.7 per cent to Dh2.98 in Dubai. The company said last week it is investing $50 million as part of a consortium to build the new Europe India Gateway, a submarine cable that will connect broadband across three continents.
But the Dubai Financial Market (DFM) fell 0.8 per cent to 1,466.83 points as most heavyweight stocks retreated.
Emaar Properties, the builder of the world's tallest skyscraper lost 2.4 per cent to Dh2.85 and Arabtec lost 1.4 per cent to Dh1.42.
The Abu Dhabi Securities Exchange was a bright spark in the region as it closed up 0.6 per cent to 2,628.31 points.
Most other markets suffered from profit-taking and foreign investors fleeing the region as new reports of protests in Oman surfaced.
Muscat's market dropped 2.8 per cent to 6,458.37 per cent.
Egypt's stock exchange will re-open on Tuesday, a spokesman for the company said yesterday. The Cairo benchmark index, the EGX 30 was shutdown after falling 16 per cent in two days in the run-up to the revolution over former President Hosni Mubarak's regime.