(Reuters) - Groupon Inc sold more than 650,000 holiday deals between Black Friday and Cyber Monday, an increase of 500 percent compared with last year, Chief Executive Officer Andrew Mason said in a blog post on Wednesday.

The largest daily deal company's shares have come under pressure in recent weeks on concerns about increased competition. The stock has fallen by nearly half since hitting a high of $31.14 after its initial public offering earlier this month.

Groupon shares rose 2.3 percent to $16.39 in early trading on Nasdaq.

LivingSocial, which is Groupon's closest rival and is partly owned by Amazon.com Inc, offered more than 20 deals with national merchants over the crucial Black Friday shopping period.

Mason, known to be outspoken, also said in his blog post that with the IPO behind it, Groupon would communicate more freely again. We're back to communicating like a normal company again ... well, as normal as we can muster at Groupon, Mason wrote.