The Opec+, as the alliance is called, cut output by 1.8 million barrels of oil per day starting January last year up to May this year to lower oil inventories and shore up prices, which plunged to less than $30 a barrel in the first quarter in 2016.
Brent dropped US$3.25 a barrel, or 4.5%, to a low of US$66.94 as of 10.40am EST (1540 GMT).
Oil prices posted the deepest plunge in more than three years in the worldwide market. He said there was now an oversupply of oil, leading to plummeting prices, and that the kingdom would curb its output to stabilize the market.
"Crude oil futures succumbed to overwhelmingly bearish pressure amidst ... weaker market fundamentals", said Benjamin Lu, analyst at brokerage Phillip Futures in Singapore. The recovery in oil prices that followed the 2017 OPEC-led supply cut is still prompting more growth in rival production. Every dollar per barrel change in crude oil prices impacts the import bill by Rs 823 crore ($0.13 billion).
Capital Economics said it was clear that "fears over excess supply in the oil market are starting to build".
Brent Crude is not down more than 20 percent from its recent high, officially putting it in bear market territory. Stockpiles in industrialized nations have increased for four consecutive months and are set to jump by 2 million barrels a day next half if current output is maintained, the agency said.
The IEA, in its monthly report, kept its forecast for global demand growth for 2018 and 2019 unchanged from last month at 1.3 million barrels per day and 1.4 million bpd, respectively.
Oil prices, which spiked in October in the run-up to the reimposition of United States sanctions on Iran's oil industry on November 5, fell after the USA granted waivers to eight countries importing Iranian crude for a 180-day period.
Opec is meeting on December 6 and is expected to decide then whether to carry on the production cuts.
Riyadh indicated on Monday it was on course to ignore the U.S. president's wishes at OPEC's next meeting due in December because it saw a need to reduce OPEC output by a collective one million barrels per day during 2019.
The rise in USA production is contributing to higher stockpiles.