NEW DELHI: Crude oil prices dived 31 per cent within hours, the worst since Gulf war in 1991, triggering a rout in domestic stocks on Monday. Snowballing of YES Bank crisis only fanned investor fears.At 1 pm, the BSE Sensex was trading 2009.20 points, or 5.375 per cent, lower at 35,567.42 Nifty plunged 547 points, or 5.11 per cent, to 10,431. The crash in market wiped off Rs 6.35 lakh crore from the total market capitalisation of BSE-listed companies as it fell to Rs 137.95 lakh crore.While a steep fall in crude oil prices could be a boon for India, which runs a trade deficit and has high inflation, a steep fall in crude prices also paints a weak outlook for the world economy.“Oil output cut was already factored in. But Opec+ talks failing shocked the market,” said Azlin Ahmad of Argus Media.Ahmad said that crude prices may fall further in days to come and it is hard to say where the floor is.Shares of the most-valued firm Reliance Industries tanked 10 per cent to Rs 1,142.95 . Stocks of oil marketing companies HPCL, BPCL and IOC gained up to 8 per cent."In case of oil price correction, India is winner. But whenever there is a global economic slowdown , India has never been a winner. If oil is going down partly because demand is very weak, that does not help any economy and India is no exception," said Arvind Sanger, Geosphere Capital Management.Investors were also concerned over the impact of YES Bank on the financial sector as a whole. Private sector lender IndusInd Bank has announced a deferment of its plans to raise funds using additional tier-1 instrument. The scrip was down 6.39 per cent at Rs 949.50. Indiabulls Housing said YES bank owes Rs 662 crore to the housing finance company in the form of bonds. The stock fell 12.68 per cent to Rs 222.15.The CBI has in fact booked YES Bank co-founder Rana Kapoor, DoIT Urban Ventures, a company allegedly held by his family members, and DHFL promoter-director Kapil Wadhawan for alleged criminal conspiracy, cheating and corruption. Shares of DHFL fell 5 per cent to Rs 15.89.YES Bank surged 20 per cent in early trade, only to retreat. The stock was up 7 per cent at Rs 17.40. State Bank of India said it will pick up a 49 per cent stake in YES Bank for Rs 2,450 crore and clarified that all the deposits and liabilities of the reconstructed bank will continue in the "same manner". Shares of SBI declined 3 per cent in early trade.Earlier in the day, oil prices fell by the most since 1991 after Saudi Arabia kicked off a price war with Russia by slashing its selling prices. The oil-rich nation pledged to unleash its pent-up supply onto a market reeling from falling demand because of the coronavirus outbreak.Brent crude futures fell by as much as $14.25, or 31.5 per cent, to $31.02 a barrel. That was the biggest percentage drop since Jan. 17, 1991, at the start of the first Gulf War and the lowest since February 12, 2016.Fresh cases in Italy, Germany and France and Italy have raised concerns over the virus outbreak. In Italy alone, the death toll soared from 133 to 336 people in a single day. On the other hand, Iran's health ministry on Sunday reported 49 new deaths from coronavirus.The overall confirmed cases on the mainland China stood at 80,735 by the end of Sunday, which included 3,119 people who have died so far.