"The cause of today's network issue is in certain nodes in the core network resulting in network disturbances for a limited number of customers across the world, including in the UK," Ericsson UK and Ireland CEO, Marielle Lindgren, said in a statement. "We have been working hard on resolving the UK data issue since early this morning. The faulty software that has caused these issues is being decommissioned. Our priority is to restore full data services on the network by tomorrow morning." The company also apologized for the inconvenience.

O2 said that services are slowly being restored and the company would continue to work on the problem throughout the night. O2 has 32 million customers on its network while SoftBank hosts 40 million mobile customers. O2 customers impacted by the outage aren't able to access data and the company said they may experience "intermittent issues" when making voice calls as well.

"I want to let our customers know how sorry I am for the impact our network data issue has had on them, and reassure them that our teams, together with Ericsson, are doing everything we can," said Telefonica UK (O2) CEO Mark Evans. "We will continue to work with Ericsson, through the night, who have assured us that a full service will be restored for customers by the morning. We fully appreciate it's been a poor experience and we are really sorry."

Ericsson said in a press release that most services had been restored.