The BSE benchmark Sensex plunged by 260 points to close at nearly four-week low of 25,329.14, tracking global sell-off sparked by escalating geopolitical tensions after US President Barack Obama authorised targeted air strikes in Iraq.

The broader 50-issue NSE Nifty stumbled by 80.70 points or 1.06 per cent to end below 7,600-mark at 7,568.55. Previously, it had finished at 7,526.65 on July 15, 2014.

Brokers said the sentiment was also hit by the rupee slumping to five-month low of 61.74 (intra-day) against the US dollar with global crude prices shooting up.

The rupee plunged by 52 paise to five-month low of 61.74 against the dollar, but the domestic currency managed to close seven paise higher at 61.15 on suspected RBI intervention in the Forex market.

After opening lower by over 180 points, the 30-share Sensex at one point was down over 350 points before ending the day at almost four week low of 25,329.14 --a level not seen since July 15--registering a steep loss of 259.87 points or 1.02 per cent.