The 30-scrip index rose as much as 277 points to touch 36,894 in early trade, while the Nifty climbed 84 points to 11,018. Gains were led by buying in IT and media stocks.
The Nifty had last crossed the 11,000 mark in intraday trade on October 1. At 9:55 am, the Sensex traded 265 points higher at 36,882 while the Nifty was at 11,012, up 77 points from the previous close.
Top advancers on the Nifty50 were Tech Mahindra, Zee, Hindustan Petroleum and Indiabulls Housing Finance, trading between 1.6 per cent and 5 per cent higher.
Tech Mahindra shares jumped as much as 5.8 per cent to hit an intraday high of Rs. 794.60 apiece on the NSE in morning deals, a day after the IT company reported its earnings for the quarter ended December 31, 2018.
The software services exporter's profit increased 13 per cent sequentially to Rs. 1,203 crore in the October-December period, beating analysts' estimates.
Among other large cap companies that reported their earnings on Wednesday were GAIL, Hindustan Petroleum (HPCL) and Punjab National Bank (PNB).
Shares in Punjab National Bank rose 1.4 per cent on Thursday, extending their gains after the state-run lender reported a surprise profit for the December quarter on lower bad loan provisions.
Meanwhile, equities in other Asian markets logged mild gains amid cautious traded as investors waited to see if US President Donald Trump drops any hints of progress on tariffs in his State of the Union speech.
MSCI's broadest index of Asia-Pacific shares outside Japan was flat with China and several other markets in the region still closed for the Lunar New Year holiday. Japan's Nikkei edged up 0.3 per cent, while E-Mini futures for the S&P 500 barely budged.
Analysts awaited the outcome of the RBI's policy meeting due on Thursday.
With consumer inflation below its medium-term goal, many economists expect the central bank to change its policy stance in preparation for a rate cut in the next policy meet due in April.
A higher closing for the Sensex and Nifty on Wednesday would mark the fifth straight day of gain for the benchmark indices. The Sensex and Nifty have added 1,025 points (2.9 per cent) and 282 points (2.7 per cent) in past four sessions.