According to an the Skype network uses what it calls "supernodes" which act as directories for finding users online. On Wednesday many of these supernodes were taken offline by a problem affecting some versions of Skype, the company said.

"Our engineers are creating new 'mega-supernodes' as fast as they can, which should gradually return things to normal," the company blog post said, adding that it may be several hours before the service returns to normal. Services such as group video calling may be offline longer.

In a status update, the company noted that "Enterprise products including Skype Connect and Skype Manager continue to function normally."

Reliably serving paying corporate customers is considered key to the success of the company, which is preparing for an initial public offering. The majority of Skype users pay nothing to use the service.