Sensex crossed the psychological 8,400-point mark within minutes after the trading session commenced on Monday. The benchmark 30-share index scaled a new all-time intraday high of 8,419.41 on the back of robust buying interest in a number of pivotal stocks across various sectors.

The markets opened on a firm note on Monday, while continuing with the northward record-breaking rally being witnessed on the bourses. The market observers were expecting the Sensex to hit the 8,400 mark on Monday. The index had scaled record highs at both intraday and closing levels on Friday last week.

However, some market analysts expect the recent reports of government planning to increase its monitoring of the current rally and the Left parties smelling a stock market scam in offing to lead to some cautiousness among the investors.

The market sentiments gained support in morning trade from continuing strength in inflows from FIIs and an uptrend in the buying activities by the domestic mutual funds. The recent Sebi decision to permit full access to mutual funds to the F&O segment has also boosted the market sentiments. According to the latest data, FIIs were net buyers of Rs 407.20 crore on Thursday.

A robust performance from Indian ADRs on Friday last week also boosted the positive momentum on the bourses. Among the Indian ADRs, Dr Reddy's Labs, HDFC Bank, ICICI Bank, Infosys, Satyam Computer and Tata Motors moved higher, while Wipro closed in negative territory on Friday.

On Monday, private banking major HDFC Bank, engineering and construction major L&T, aluminium and copper major Hindalco Industries and Pharma majors Cipla, Ranbaxy and Dr Reddy's Labs were trading with robust gains in early morning trade.

However, Bharti Tele, Reliance Industries (RIL), Wipro and Grasim Industries were trading on a subdued note.