* 2nd-qtr adj. profit $12.51/share vs est. $12.04
* Revenue rises 26 pct
* International gross bookings rise by more than a third
* Shares rise as much as 4 pct
(Adds CEO, analyst comments; updates shares)
Aug 11 (Reuters) - Online travel agency Priceline Group Inc reported a better-than-expected quarterly profit due to a jump in international bookings for hotels, airlines and rental cars at the start of the summer travel season.
Total gross bookings rose 34 percent in the second quarter. International bookings jumped more than a third, accounting for 86 percent of total bookings. (http://bit.ly/1q4NVUe)
Priceline has been stepping up investment in its international markets amid rising competition from rivals Expedia Inc and Orbitz Worldwide Inc.
Priceline said last week that it would invest $500 million in China's Ctrip.com International to give customers access to more than 100,000 places to stay in the Greater China region.
"Priceline has always had success developing standalone brands that they have acquired, particularly when that brand has struggled internationally," said Benchmark Co analyst Daniel Kurnos. "That's one of their specialties."
Priceline bought restaurant reservation website OpenTable in June in an attempt to become a one-stop shop for travelers.
The company, which plans to increase its investment in OpenTable in the third quarter, has launched mobile apps to reserve tables through OpenTable in New York. Priceline said it would launch the app in 20 U.S. cities before the end of the year.
"They have an opportunity to invest in the back half of the year, which they are going after," Kurnos said.
Priceline said net profit available to common shareholders rose 32 percent to $576.5 million, or $10.89 per share, in the second quarter ended June 30.
Excluding items, the company earned $12.51 per share.
Revenue rose 26 percent to $2.l2 billion.
Analysts on average had expected earnings of $12.04 per share on revenue of $2.15 billion, according to Thomson Reuters I/B/E/S.
Priceline, however, forecast third-quarter profit below analysts' estimates as it spends on expansion.
The company said it expected an adjusted profit of $19.60-$21.10 per share for the third quarter ending Sept. 30. Analysts on average were expecting $21.28 per share.
Priceline's shares were up 2.8 percent at $1,317.58 in late morning trading on the Nasdaq.
The stock trades at 21.5 times its 12-month forward earnings and is expensive compared with shares of Expedia and Orbitz, which trade at an average of 19.9 times, according to Thomson Reuters data.
(Additional reporting by Ankit Ajmera in Bangalore; Editing by Kirti Pandey)