The Australian stock market has suffered its worst single day loss in nearly a dozen years, as a brewing price war over oil added to the global tumult.
The benchmark S&P/ASX200 index shed about $155 billion in value on Monday, plunging 455.6 points, or 7.33 per cent, to a two-year low of 5,760.6.
The broader All Ordinaries index finished down 465.1 points, 7.4 per cent, to 5,822.4.
In percentage terms, it was the ASX200's biggest loss since an 8.34 per cent drop on October 10, 2008, when markets had a meltdown during the GFC.
In points terms, the 456-point drop was the ASX200's biggest loss ever.
"Wholesale panic," said CMC Markets chief market strategist Michael McCarthy.
"They're coming in and selling hard."
The energy sector plunged a shocking 20 per cent as Saudi Arabia and Russia both promised to boost oil production in what looked to be the start of a new price war.
The price of Brent crude, which had traded as high as $US68 a barrel in January, plunged from $US46 on Friday to as low as $US31.48 on Monday.
Woodside Petroleum dropped 18.4 per cent to a 15-year low of $21.54, Oil Search plunged 35.2 per cent to a 15-year low of $3.30, and Santos fell 27.0 per cent to a two-and-a-half-year low of $4.89.
"These are extraordinary moves for individual stocks," Mr McCarthy said.
In the mining sector, BHP plunged 14.4 per cent to a two-and-a-half-year low of $27.55, while Rio Tinto dropped 6.4 per cent to $80.77 and Fortescue Metals declined 10.6 per cent to $8.58.
Goldminer Newcrest rose 2.5 per cent as the price of the precious metal traded at $US1,664 an ounce after breaking the $US1,700 barrier over the weekend for the first time since early 2013.
But other goldminers dropped, with Saracen Minerals, Gold Road Resources and St Barbara all down between 5.8 and 11.2 per cent.
All the major banks sold off heavily as well, with Commonwealth dropping 6.5 per cent to a one-year low of $69.15 and its smaller rivals in the big four hitting their lowest levels since 2012.
ANZ and NAB both skidded 8.5 per cent, to $20.27 and $20.14 respectively, while Westpac dropped 8.6 per cent to $19.52.
Federal Treasurer Josh Frydenberg sought to calm things down, saying market volatility was not uncommon in times like these and there were a number of factors at play.
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But Wall Street looked to be headed for a major sell-off as well when the market opened.
Futures on the S&P 500 Index stopped trading after falling five per cent, triggering "circuit breaker" limits that prevented further falls.
With Monday's decline, the ASX is now down 13.8 per cent for the year, having dropped 19.9 per cent in just 12 and a half days of trading from its February 20 all-time intraday peak.
An early afternoon flash crash also sent the Aussie dollar plummeting to a new 11-year low against the US greenback, with the local currency diving from 66 US cents to a low of 63.11 US cents.
At 1711 AEDT, it had bounced back to 65.46 US cents.
Against the Japanese currency, the Aussie was down 2.5 per cent to a more than decade low of 67.20 yen.