Millions of O2 customers have been left without coverage after their network went down.
The operator say 31 million mobile users have been affected by the outage, which began around 6am this morning.
The company tweeted at 7:30am after customers reported being unable to access the internet and other services due to a fault with the company network which impacted mobile data.
The company said that the problem stemmed from a global software issue with third-party supplier Ericsson, which has also affected other mobile operators around the world.
We are aware our customers are unable to use data this morning. Our technical teams are working on the issue with high priority. We are really sorry and working as hard and as fast as we can to fix this. Please keep an eye on our status checker: https://t.co/O8fb26fNIv
— O2 in the UK (@O2) December 6, 2018
More than 25 million O2 customers have been hit by the problem which affects several other mobile networks, including Sky, Tesco and Giffgaff, bringing the total affected to 31 million.
O2 said fixing the issue remains a "top priority" but admitted that they do not know when the service outage will end.
Outage Update: Our teams are working closely with one of our 3rd party suppliers who has identified an issue in their system which has impacted mobile services globally. This is our top priority and we are really sorry. Get updates here: https://t.co/5oS7qap2bj
— O2 in the UK (@O2) December 6, 2018
A spokesperson for O2 said: "The network issue we are currently experiencing remains a top priority for us and we are working as quickly as possible to fix the issue.
"All O2 technical teams are working closely with one of our third party suppliers who has identified a global software issue in their system which has impacted data services.
"As a result of this incident, we are experiencing a high demand on our network which means some customers may have issues making and receiving voice calls.
"We believe other mobile operators around the world are also affected.
"We apologise to our customers for any inconvenience."
