Vodafone appears to be suffering a major outage, with mobile and home broadband customers across the UK claiming they are unable to access the network.
Problems started at around 14:42 BST, according to website DownDetector, which monitors online outages.
Customers in London, Glasgow, Manchester, Birmingham, Nottingham, Bristol, Liverpool and Leeds have all reported issues.
Elsewhere in Europe, Vodafone customers in Spain, Ireland, Italy, Germany, Greece and Portugal are also experiencing problems.
"Massive Vodafone outage right now affecting European users at least," tweeted Ian Kenefick, senior cyber security engineer at Trend Micro.
Vodafone acknowledged the outage via its Irish Twitter account.
"We are currently investigating a potential outage to our fixed and mobile services," the company tweeted. "We thank you for your patience as we work to get this resolved."
Vodafone has around 19.5 million customers in the UK, and almost 444 million worldwide.
Hundreds have taken to social media to complain about the outage:
Vodafone is yet to comment on the cause of the outage.
One commenter on DownDetector suggested the problem was to do with Vodafone's DNS servers, which help to route traffic across the network.
"Change you DNS or DNS Forwarder to Google's Public one 8.8.8.8 and you will get most of the Internet back," he said.
Developing...
