State Bank of India, the nation's top lender by assets, reported a better-than-expected 25 percent increase in quarterly profit on the back of higher interest income and a drop in bad loans, driving its shares up over 4 percent.

Net profit rose to 38.79 billion rupees ($589.5 million) for its second quarter ended Sept. 30, from 31 billion rupees a year earlier, SBI said in a statement on Friday.

Analysts on average had expected the lender to report a net profit of 36.39 billion rupees, according to data compiled by Thomson Reuters.

Gross bad loans as a percentage of total loans dropped to 4.15 percent from 4.29 percent in the June quarter. Provisions for bad loans dropped almost 7 percent.