A significant number of people are still unable to use the Skype Internet communication service nearly 24 hours after technical glitches brought down the company's network. 

Around 9 a.m. EST Thursday morning, the company Tweeted that as many as 10 million users were now able to use the service, although the company recently announced a peak usage of 25 million. This means as many as 15 million people are still unable to access the telephony network -- and advanced services such as group video calling may take longer to restore.

"In the last hour, we've seen evidence of a significant increase in the number of people online," the company wrote in a blog post. "Because of the way the Skype software works, it's not possible for anyone to obtain an exact figure, but we now estimate it to be over 10 million."

Users across the globe reported issues accessing the service Wednesday morning, prompting the company to acknowledge the issue on Twitter: "Some of you may have problems signing in to Skype -- we're investigation, and we're sorry for the disruption to your conversations."

Skype followed up with another Tweet assuring users that their "engineers and site operations are working non-stop to get things back to normal."

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The problem is unconnected to the hacking attacks that disabled popular websites such as MasterCard and Visa in recent weeks. Chaim Haas, a spokesman for Skype, explained to FoxNews.com that the company's telephony network relies on millions of individual connections between computers and phones to stay up and running, referencing a blog post by the company.

"Under normal circumstances, there are a large number of supernodes available," network features which act like phone directories for Skype, Haas said. "Unfortunately, today, many of them were taken offline by a problem affecting some versions of Skype."

Engineers created new "mega-supernodes" that solved the problem, Haas said. As of about 3:30 p.m. EST, normal services had started returning to Skype, the company said, acknowledging that it may take "several more hours" before all users can sign in again.

Later that day, the company Tweeted again -- this time a request for patience. 

Luxembourg-based Skype was founded in 2003 as an alternative to the standard telephone network by transmitting voice, video, and text conversations the Internet.

In August, Skype announced plans to raise up to $100 million in shares by listing on the NASDAQ stock exchange. Last month, the company announced a new milestone in traffic, with 25 million concurrent users.

On Tuesday, Skype CEO Tony Bates detailed the company's plans for expansion with MercuryNews.com. He hopes to charge consumers for unspecified "premium services," attract new users, and extend the service onto TV and mobile devices.

The last major outage occurred in 2007 and lasted an entire day.