BENGALURU, Feb 16 Reuters Indian shares rose on Friday, set to extend gains for the fourth straight session, led by the auto sector39;s surge on Mahindra Mahindra39;s postresults rally and a jump in Tata Motors.

The NSE Nifty 50 index was up 0.53 at 22,026.75, while the SP BSE Sensex added 0.49 at 72,400.98, as of 1026 a.m IST.

The benchmarks have each added about 1 so far this week.

Eleven out of the 13 major sectors logged gains, with forty of the Nifty 50 stocks advancing. The broader, more domesticallyfocussed small and midcap indexes rose 0.8 and 0.4, respectively.

Despite the continuing outperformance of small and midcaps, the shift to largecaps is imminent, and could power the benchmarks further, said Pramod Gubbi, cofounder of Marcellus Investment Managers.

The auto index gained 2, led by a postresults jump in Mahindra Mahindra and supported by Tata Motors amid a report of a potential spinoff of its battery business by the Tata Group.

Both Mahindra Mahindra and Tata Motors rose about 2.5 each, and were among the top five Nifty 50 gainers.

The pharma index advanced 1.50, aided by a recovery in Aurobindo Pharma following a decline earlier in the week on regulatory worries over its U.S. unit, as well as a postresults rally in several key constituents.

Oil marketing company OMC Bharat Petroleum Corporation increased 3.5 after Jefferies upgraded the stock to buy from hold and raised the target price to a street high of 890 rupees from 415 rupees earlier….