BENGALURU, Feb 16 (Reuters) - Indian shares rose on Friday, set to extend gains for the fourth straight session, led by the auto sector's surge on Mahindra & Mahindra's post-results rally and a jump in Tata Motors.

The NSE Nifty 50 index was up 0.53% at 22,026.75, while the S&P BSE Sensex added 0.49% at 72,400.98, as of 10:26 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 domestically-focussed small and mid-cap indexes rose 0.8% and 0.4%, respectively.

"Despite the continuing outperformance of small and mid-caps, the shift to large-caps is imminent, and could power the benchmarks further," said Pramod Gubbi, co-founder of Marcellus Investment Managers.

The auto index gained 2%, led by a post-results 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 post-results 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.

"Range bound oil prices and government staying away from auto fuel pricing have seen OMCs rally about 90%-130% since October," Jefferies said, adding that BPCL offered the largest margin of safety among OMCs.

(Reporting by Bharath Rajeswaran and Nandan Mandayam in Bengaluru; Editing by Rashmi Aich and Dhanya Ann Thoppil)