Mumbai: The BSE benchmark Sensex extended gains for the second straight day by adding over 18 points in early trade on Tuesday on selective buying by funds and retail investors ahead of the RBI' monetary policy review for 2012-13.

The 30-share index, which had gained 56.44 points in the previous session, added another 18.23 points, or 0.11 percent to 17,169.18.

The wide-based National Stock Exchange index Nifty also traded marginally up by 4.40 points, or 0.08 percent, to 5,230.60.

Brokers said investors turned cautious ahead of the Reserve Bank of India's meeting on Tuesday on interest rate and made selective buying.

Stocks of Metal, Realty and Auto sector were trading in the positive zone.

In the Asian region, the Japan's Nikkei was up 0.06 percent, while Hong Kong's Hang Seng shed 0.06 percent in the morning trade on Tuesday. The US Dow Jones Industrial Average ended 0.56 percent higher in on Monday’s trade.