In the worst crash this year, the benchmark Sensex today broke below the 25,000-level by tanking about 555 points to close at 24,851.83, a 19-month low, as global stock and currency markets reeled after China let the yuan fall faster to battle a slowing economy.

The NSE Nifty too plunged headlong as it went below the 7,600-mark by falling 172.70 points, or 2.23 per cent, on massive selling across sectors.

Realty, infrastructure, auto, metal and capital goods were among the worst hit as investors got anxious amid a global sell-off. Power, PSU, oil and gas and banking shares also came under pressure.

The 30-share BSE index resumed the day sharply lower in line with the global sell-off and remained weak throughout as selling intensified. The gauge ended with a steep fall of 554.50 points, or 2.18 per cent, at 24,851.83, its lowest closing since June 4, 2014, when it closed at 24,805.83. Intra-day, it hit a session's low of 24,825.70.

The Sensex has now lost 1,309.07 points in four straight sessions.

Asian markets were in deep red, with Shanghai shares crashing 7.32 per cent, forcing authorities to suspend trading less than half an hour after opening as the new circuit-breaker tripped for the second time in a week.

The fall came amid worries over a slowing growth in the world's second-largest economy, which has roiled investors worldwide, and pressure on its currency from capital outflows.

China's central bank today lowered the yuan against the US dollar by 0.51 per cent to 6.5646, the lowest since March 2011.

After getting below the 7,600-mark, the NSE Nifty touched the day's low of 7,556.60 before settling at 7,568.30, a sharp fall of 172.70 points, or 2.23 per cent.

All the 30-Sensex constituents led by BHEL (6.98%), Tata Steel (6.85%) and Tata Motors (6.15%) ended in the negative territory.

The sell-off also sparked losses in Axis Bank, Maruti Suzuki, ONGC, SBI, Adani Ports, L&T, Bajaj Auto, Hindustan Unilever, NTPC, Hero MotoCorp, M&M, HDFC Ltd, Lupin, Cipla, RIL, Dr Reddy's and ITC, falling up to 4.98 per cent.

In the forex market, the rupee was trading at a fresh two-week low of 66.90 against the dollar (intra-day).

Sentiment further got dampened after global crude prices softened to multi-year lows following China's weakening currency and rising global stock reserve.

The US benchmark crude contract slid below USD 34 a barrel while Brent fell to USD 33.61 per barrel.

The BSE realty index suffered the most tumbling 4.50 per cent, followed by infrastructure 3.91 per cent, auto 3.72 per cent, metal 3.72 per cent and power 3.45 per cent.

In line with the overall trend, the BSE small-cap and mid-cap indices plunged 2.87 and 2.61 per cent, respectively.

The weakness in Shanghai's composite index triggered an Asian share slump of 7.36 per cent following overnight losses in US markets.

Foreign portfolio investors net sold shares worth Rs 242.48 crore yesterday, provisional data showed.