India's blue-chips fell for the sixth session in a row on Thursday, as the selling pressure intensified due to elevated U.S. Treasury yields and concerns over the Middle East conflict.

The NSE Nifty 50 index settled 1.39% lower at 18,857.25, its first close below the 19,000 mark since June 28. The S&P BSE Sensex fell 1.41% to end at 63,148.15.

The benchmarks have lost nearly 5% over the last six sessions, which pushed the Nifty into oversold territory for the first time in 16 months.

Only four of the Nifty 50 stocks advanced on the day.

All 13 major sectoral indexes logged losses. The high-weightage banks and IT sectors lost 1.29% and 1%, respectively.

The slide in IT stocks was led by Tech Mahindra's 2.34% decline after it posted its biggest fall in profit in over 16 years.

Adani Enterprises lost 2.38%. Reuters reported that India's accounting regulator had started an investigation into one of the Adani group's auditors.

Even the small- and mid-caps, which had been outperforming their larger peers, fell, losing 0.34% and 1.16%, respectively.

The sell-off was region-wide, with the MSCI Asia ex-Japan index shedding 1.25%.

India's volatility index jumped 3.69% to 11.73 at the close, its highest in over three weeks.

"Domestic equities have been under pressure over the past two weeks because of worries that if the (Middle East) conflict continued for a long time, it would have adverse repercussions for the global economy and markets," said Avinash Gorakshakar, head of research at Profitmart Securities.

"Elevated U.S. treasury yields could trigger an extended period of foreign outflows," he added.

Asian Paints and McDonald's franchisee Westlife Foodworld shed 3.28% and 1.81%, respectively, after missing profit estimates for the second quarter.

Private lender Axis Bank gained 1.74% after it beat profit estimates for the September quarter on strong loan growth.

(Reporting by Bharath Rajeswaran in Bengaluru; Editing by Varun H K and Savio D'Souza)