Domestic stock markets tumbled more than 1 per cent on Monday amid unease over a new coronavirus strain that was shutting much of the United Kingdom, halting a rally last week that took the benchmark Nifty 50 index above the 13,750 mark for the first time ever. The Sensex index dropped 648.49 points, or 1.38 per cent, to hit 46,312 at the weakest level recorded during the session, and the broader Nifty benchmark plunged to as low as 13,548.75, down 211.8 points, or 1.54 per cent, from its previous close. A selloff across sectors — led by banking, financial services, automobile and metal shares — dragged the markets lower. ONGC, GAIL, Indian Oil, IndusInd Bank, Tata Motors and Tata Motors, trading between5.95 per cent and 7.88 per cent lower, were the worst hit among 50 laggards in the Nifty basket of 50 shares. HCL Tech, Infosys and Nestle – up 0.36-0.68 per cent each – were the top Nifty gainers. ICICI Bank, ITC, Larsen & Toubro and SBI were the biggest drags on Sensex. The four accounted for more than 250 points in the loss in the 30-scrip index.