The plunge in the first day of trading in the Muslim week also follows heavy losses in global bourses on Friday when Gulf exchanges are closed for the weekend.
The price of oil, which contributes more than 80 per cent to Gulf states' revenues, shed more than 20 per cent this year to drop below USD 30 a barrel. This follows a plunge of 65 per cent in the past two years.
Qatar and Dubai bourses led the slide, diving 6.0 per cent at the opening before easing slightly.
The Dubai Financial Market was trading down 5.6 per cent to below the 2,700-point mark. Blue chips properties giant Emaar and leading construction firm Arabtec dropped 4.4 per cent and 5.2 per cent.
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The Qatar Exchange, the second largest in the Gulf after Saudi Arabia's, fluctuated sharply within minutes after opening. Less than hour after the start, the bourse was trading down 5.0 per cent below the 8,800-point level.
The Kuwait Stock Exchange dropped 2.4 per cent to just above the 5,000-point mark, levels only seen in 2004.
The Saudi market was to open at 0800 GMT.
The small market of Oman dropped 1.5 per cent and Bahrain 0.3 per cent.
All Gulf stock exchanges ended 2015 in negative territory, led by Saudi Arabia, after the sharp decline in oil prices.