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Markets are in turmoil after the collapse of an alliance between Saudi Arabia and Russia, two of the world's top oil producers, triggered the worst one-day crash in oil prices in nearly 30 years — fanning new fears about a global economy already reeling from the coronavirus pandemic.

What's happening: Saudi Arabia slashed oil prices after Russia refused to go along with OPEC's proposal to impose deeper cuts to production in the face of slumping demand. The standoff sent Brent crude futures, the global benchmark, down as much as 31% to $31.02 per barrel, as traders brace for Saudi Arabia to flood the market with crude.

The shock has also rattled stock and bond markets , which were already freaking out over the global spread of the coronavirus. On Sunday, Italy put much of its prosperous north — including financial capital Milan — on semi-lockdown, the most dramatic effort yet to contain the virus outside China.

Italy's main stock index plunged more than 9% in early trading, while Germany's DAX and Britain's FTSE 100 have both lost more than 6%. S&P 500 futures fell by as much as 5% in early trading in Asia, their upper limit.

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