Internet coupons seller Groupon raised $700 million after increasing the size of its initial public offering, becoming the largest IPO by a US Internet company since Google raised $1.7 billion in 2004.

The global leader in 'daily deals' is now valued at almost $13 billion after saying it increased the offering by 5 million shares to 35 million in total and pricing them at $20 each, above an initial range of $16 to $18.

The debut of the three-year-old company, which sells Internet coupons for everything from spa treatments to nose jobs, is one of this year's most closely watched. Its tiny float represents just above five per cent of the company and helped drive up demand and price.

That constraint - one of the smallest floats of the past decade - should support Groupon's share price when it begins trading on the Nasdaq.

But in the longer run, there are concerns about competition from the deep-pocketed likes of Google and Amazon.com, the need to spend continuously to drive user growth, and questions about accounting after the company altered its IPO filings twice to change the way it accounted for revenue.

LinkedIn, which remains well above its $45 IPO price, plummeted 9 per cent after-hours after unveiling a proposal to sell up to $500 million in stock. It had floated 8.3 per cent of its shares during the IPO.

Pandora Media, a music streaming service and another recent dotcom debutante, sold 9.2 per cent of the company.

At $12.8 billion, Groupon commands a price tag more than twice what Google offered to buy the company last year.

If underwriters, led by Morgan Stanley, Goldman Sachs and Credit Suisse, exercise their right to buy just over 5 million more Groupon shares in the IPO, known as the greenshoe, Groupon will raise more than $800 million, before fees.

Wall Street will scrutinise Groupon's showing for clues as to how other highly anticipated dotcom IPOs - from the likes of Facebook or Zynga - may fare.-Reuters