Saudi Arabia's stock market tumbled again early on Thursday, hit by the plunge of oil to new 11-year lows and investor worries about the health of the regional and global economies.

Brent crude futures sank more than 4 percent to below $33 a barrel for the first time since April 2004. The Saudi equities benchmark fell 3.1 percent in the first 10 minutes of trade to new three-year lows; stocks were dumped across the board.

Saudi Basic Industries, the bourse's largest stock by market value, slid 5.3 percent.

"The multi-year low oil prices, weak demand in key markets and the recent change in feedstock prices are expected to significantly impact the petrochemical sector's expected profitability in 2016," said a note by Riyadh-based NCB Capital.

The seasonally adjusted Emirates NBD Saudi Arabia Purchasing Managers' Index, which measures growth in the non-oil private sector, fell to 54.4 points in December, its lowest since the survey was launched in August 2009.

The banking sector was also caught in panic selling with Arab National Bank leading declines, tumbling 5.6 percent.

Qatar's index sank 2.2 per cent to 9,852 points in the opening minutes of trade, approaching technical support on its December low of 9,614 points.

Selling was broad-based, but the biggest losers included oil-related stocks such as drilling rig provider Gulf International Services, which was the most heavily traded stock and tumbled 4.6 percent. Petrochemical producer Industries Qatar lost 3.4 percent.

Dubai's index was down 3.3 per cent at 2,970 points after nearly an hour of trade, still testing fresh lows. It has technical support at the December low of 2,851 points. Selling was indiscriminate, with blue chip Emaar Properties losing 4.4 percent.

Abu Dhabi's index, which is usually less liquid and volatile than Dubai, dropped 1.3 percent, with real estate shares leading declines.

Purchasing managers' surveys released on Thursday showed business activity growth in the United Arab Emirates' non-oil private sector slowed to a 40-month low in December. Growth in Saudi Arabia's non-oil private sector slowed to its lowest since the survey began in August 2009. - Reuters