Aug 3 (Reuters) - India's Nifty 50 (.NSEI), opens new tab and BSE Sensex (.BSESN), opens new tab showed a rare divergence on close of trade on Monday as exchanges adopted a new auction ​mechanism for stocks with traded futures and option contracts.

The Nifty was up 1.6% ‌at 24,774.30 as of 3:30 p.m. IST on Monday. The BSE Sensex (.BSESN), opens new tab closed 0.7% higher at 78,639.03.

The displayed Nifty level was the official closing level, a source familiar with the matter said, adding there was no trading ​glitch.

SEBI's new Closing Auction Session (CAS), effective Monday, replaced the earlier method of calculating ​closing prices for stocks in the futures and options segment where closing prices were ⁠based on the volume-weighted average price of trades during the final 30 minutes of continuous ​trading.

Under CAS, buy and sell orders placed near the close are matched in a single-price auction, ​with the resulting price becoming the official close.

The change is intended to produce a fairer and more transparent closing price by concentrating end-of-day liquidity in one auction, rather than relying on trading across the final ​half-hour.

"It appears to be a single, end-of-session price movement that has caused the divergence between ​the benchmarks," said Siddhartha Khemka, head of research for wealth management at Motilal Oswal Financial Services.

"We are waiting ‌for ⁠a response from the NSE and other market participants are also trying to understand the anomaly and are awaiting clarification from the NSE on whether it is related to the Closed Auction Session."

India's equity benchmarks closed higher for a fourth consecutive session on ​Monday, with Nifty 50 ​ending at a ⁠five-month high and Sensex settling at over three-month high.

A 5% drop in Brent crude prices, encouraging earnings season, and a pullback in Asia ​chip stocks lifted sentiments.

Brent crude fell 5% to $83.55 a barrel after U.S. ​President Donald ⁠Trump said talks with Iran would happen on Monday but declined to set a deadline for an agreement.

All the 16 major sectors advanced, while the broader small-cap (.NIFSMCP100), opens new tab and mid-cap (.NIFMDCP100), opens new tab indexes rose 1.3% and ⁠1.2%, respectively.

Information ​technology stocks (.NIFTYIT), opens new tab jumped 3.3% and were top sectoral gainers ​in India on Monday, while losses in key chip stocks pushed South Korea's Kospi down 5%.