* Q2 net profit 23.5 bln rupees vs 21.9 bln analyst estimate

* Rise led by higher credit growth

* Net interest margin at 3.31 pct vs 3.00 pct year earlier

(Adds more figures from the earnings release, analyst comments, shares)

By Swati Pandey

MUMBAI, Oct 25 (Reuters) - ICICI Bank Ltd ICBK.NS , India's largest private-sector lender by assets, beat analyst estimates by posting quarterly profit gain of around 20.1 percent, as an appetite for cars and homes led to higher credit growth.

ICICI is trying to emulate the success of rival HDFC Bank Ltd HDBK.NS with a renewed push into consumer loans as demand from the corporate sector slows in tandem with the economy.

Net profit rose to 23.5 billion rupees ($382.63 million) in July-September from a year earlier. That compared with a 21.9 billion rupees estimate of 23 analysts polled by Thomson Reuters.

Net interest income, or the difference between interest earned and paid, rose about 20 percent to 40.4 billion rupees, the bank said on Friday.

Shares of ICICI, which the market values at $19 billion, fell 17.5 percent in the September quarter, in line with the broader bank index .NSEBANK . They were down 0.16 percent at 0744 GMT, compared with the benchmark's .BSESN 0.31 percent.

"ICICI has been growing its retail book even as competition has increased. Going forward, it will be important to see how they are able to maintain this growth and manage asset quality pressures," said Jignesh Shial, banking analyst with Mumbai-based IDBI Capital.

The bank's retail book grew 20 percent in the September quarter compared with overall loan growth of 16 percent.

"We need to see in the next four quarters how they are able to grow as the economy itself is slowing. Other banks saw pressure on asset quality so ICICI will also be affected," Shial said.

No. 2 private sector lender HDFC Bank and mid-sized YES Bank Ltd YESB.NS saw some deterioration in their loan books in the just-ended quarter, largely because of weakness in the commercial vehicle and equipment segment.

Earlier this month, HDFC Bank ended its record of posting 30 percent on-year profit growth every quarter for the last decade due to investment losses and a squeezed net interest margin.

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ICICI's net interest margin, a gauge of profitability for banks, expanded to 3.31 percent during the quarter from 3.00 percent a year earlier.

Net non-performing loans, as a percentage of total assets, rose to 0.85 percent from 0.82 percent in the prior quarter. Debt restructuring, or steps to ease payment terms for stressed borrowers, grew 15 percent on quarter.

Prolonged economic slowdown is impairing borrowers' ability to repay loans. Non-performing loans for Indian banks account for nearly 4 percent of total assets compared with a global average of 2.6 percent, according to Thomson Reuters Starmine.

($1 = 61.4175 Indian rupees)

(Reporting by Swati Pandey; Editing by Christopher Cushing)

((swati.pandey@thomsonreuters.com)(+91-22-6180 7123)(Reuters Messaging: swati.pandey.thomsonreuters.com@reuters.net)(twitter.com/swatisa ys))

Keywords: ICICI RESULTS/