Shares of Google Inc surged as much as 13.5 percent on Friday, a day after blockbuster results and signs of success in mobile and social networking revived hopes the Internet titan was getting back on a growth track.

Its shares shot up to $600.25, climbing back to pre-2011 levels on the Nasdaq. If the gain stands by the end of Friday, it would mark the biggest single-day gain for Google shares since October 2008.

Chief Executive Larry Page, who provoked grumbles by saying only a few words on the last quarterly earnings call, ticked off a string of fresh statistics on Thursday that underscored progress on several fronts, including 10 million-plus members for the two-week-old Google+ social network.

More than 135 million Android smartphones or tablets -- made by the likes of Motorola and Samsung -- have been activated. And its Chrome browser is now employed by more than 160 million users.

Analysts said that perked up sentiment in a long-pressured stock, but investors should wait and see if it can carry the momentum long-term.

At the end of the last quarter, there was what we deemed to be a significant overreaction to perceived overspending, said Morningstar analyst Rick Summer.

Now we're seeing early signs that new investments should continue to extend the runway out, he added. There's a little more optimism around these longer-term initiatives.

Google is investing heavily to arm itself in a brewing battle on several fronts: with Apple Inc and Microsoft Corp on mobile and content, and with Facebook and Twitter on the Internet, to protect its lucrative search business at a time when mobile gadgets and social media are redefining the way consumers use the Web.

But the share jump suggested Wall Street was now more willing to give Page the benefit of the doubt than just a quarter ago, when he stunned investors by cutting short an appearance on an earnings conference call.

Page appeared to have won over some investors on Thursday. The co-founder said he was committed to crafting services that people across the world use twice a day -- just like a toothbrush.

He understood the need to balance the near-term with the long term and would be cognizant of the fact that it is shareholder money that is being invested into various products. This should assuage concerns about unfettered spending, said B. Riley analyst Sameet Sinha.

PROFLIGATE SPENDING?

The results were strong despite a seasonally slow quarter, macroeconomic softness and substantially higher costs -- which are expected to continue to weigh on margins in 2011. Investors had feared Google's ever-increasing spending would eat into margins. Operating expenses leapt 49 percent to $2.97 billion in the second quarter, to about a third of revenue.

Investors will welcome his reassuring comments about fiscal discipline and product focus, said Wells Fargo analyst Jason Maynard.

Google shares were up 12.8 percent at $596.57 on Friday afternoon, off the earlier high at $600.25.

Google+, the new social networking service still in testing phase, also garnered attention from Wall Street. Maynard called Google+ a huge swing factor but said early signs of 10 million users and 1 billion items shared were encouraging.

The better-than-expected results and successful Google+ launch should stem some of the short-term stock angst about their investment and development strategy, Maynard said.

Evercore analyst Ken Sena raised his price target on the stock to $735 from $670, while Collins Stewart analyst Mayuresh Masurekar raised his price target to $725 from $680.

Jefferies raised its target on the stock to $830 from $800, while Barclays Capital lifted its target to $730 and $675.

All five brokerages kept their top ratings on the stock, which was trading at $595.80 in late morning trade.

Google shares, publicly traded since 2004, hit their all-time high of $741.79 in November 2007.

We are witnessing signs of increased competitive advantage for Google, particularly in Display and Local, with Search showing no signs of slowing, Sena said.

(Reporting by Supantha Mukherjee and Edwin Chan, editing by Gopakumar Warrier, Roshni Menon and Matthew Lewis)

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