Mumbai: Equities started the week on a distinctly weak note after the Sensex tumbled 374 points today -- the most in two weeks -- tracking global sell-off ahead of the US presidential debate and an OPEC meeting due this week.
The barometer closed at 28,294.28, a nearly 1-month low.
Also, the broader NSE Nifty broke below the 8,800-mark level.
Investors are also anxiously waiting for the upcoming monetary policy review on October 4, the first to be held under new RBI Governor Urjit Patel.
Sentiment was in tatters after heavy losses in Asia and a lower opening in Europe, mirroring weekend losses at the Wall Street due to lower crude oil prices.
The slide came on the heels of a global rally last week fuelled by relief that US and Japanese central banks had decided to maintain their easy-money policies.
Shares have lost their momentum after hitting their highest close in 18 months last week after valuations turned expensive, with most sectoral indices ending in the red.
The 30-share index stayed in the negative zone for the whole day and settled lower by 373.94 points, or 1.30 per cent -- its biggest single-day fall since September 12 -- at 28,294.28. This is the weakest closing since August 29 when it had closed at 27,902.66. It had lost 105 points on Friday.
The broader Nifty also succumbed to selling pressure and slipped below the 8,800-mark to hit a low of 8,715.10 before ending at 8,723.05, down 108.50 points, or 1.23 per cent.
"The market had mirrored the downswing in global equities which is impacted due to today's US presidential election debate. Additionally, the upcoming meeting on Wednesday of oil producers will be eagerly watched for any potential freeze in oil production, given the drop in oil prices," said Vinod Nair, Head of Research, Geojit BNP Paribas Financial Services.
ONGC was the top Sensex loser, skidding 3.84 per cent to close at Rs 250.50, followed by Tata Motors, which fell 3.22 per cent to Rs 535.55.
Others that weighed included ICICI Bank, NTPC, GAIL, Bharti Airtel, ITC, M&M, Hero MotoCorp, Hind Unilever and L&T, falling by up to 3.16 per cent.
Coal India, however, struck a contrarian note as it topped the gainers list by rising 1.19 per cent. RIL gained 0.58 per cent to close at Rs 1,109.35 after touching a 7-year high of Rs 1,128.90 on the back of strong fundamentals.
Foreign portfolio investors (FPIs) turned net sellers at Rs 299.98 crore on Friday, according to provisional data.
Out of the 30-share Sensex, 25 ended lower. Realty fell the most by 2 per cent, followed by auto 1.72 per cent, infrastructure 1.62 per cent, banking 1.56 per cent and FMCG 1.37 per cent while oil & gas and metal rose 0.08 per cent each.
Small-cap and mid-cap indices closed lower by 0.55 per cent and 0.53 per cent, respectively.
Japan's Nikkei fell 1.25 per cent and Shanghai Composite plunged 1.76 per cent while Hang Seng sank 1.58 per cent.
In Europe, most indices retreated, with London's FTSE falling 1.22 per cent, France's Paris CAC-30 1.83 per cent and Germany's Frankfurt 1.49 per cent in their early hours.