Thousands of Vodafone customers across the UK have reported its services are down.
Downdetector, which monitors web outages, showed more than 130,000 people had flagged problems affecting their Vodafone broadband or mobile network on Monday afternoon.
According to its website, the firm has more than 18 million customers in the UK, including nearly 700,000 home broadband customers.
In an updated statement on Monday evening, Vodafone apologised to customers and said its network was "recovering".
"This afternoon the Vodafone network had an issue affecting broadband, 4G and 5G services," a company spokesperson said.
"2G voice calls and SMS messaging were unaffected and the network is now recovering.
"We apologise for any inconvenience this caused our customers."
It comes after people on social media said they were struggling to access Vodafone customer service operators, amid ongoing issues affecting mobile data and broadband.
Many also said they have had difficulty accessing the company's website and app, which typically allow people to view the status of its network services.
Customers have also taken to social media to complain of "complete outages" in their area.
The issues appear to have begun for customers shortly after 15:00 BST.
Internet monitor Netblocks said in a post on X that live network data showed Vodafone was experiencing "a national outage" impacting both broadband and mobile data.
Some customers expressed being doubly frustrated by not being able to access their Wi-Fi or mobile data.
"Sort it out soon please," wrote one frustrated X user - who said they were having to use a coffee shop's Wi-Fi to access online services, without the means to do so using their mobile data or broadband.
Another said they were self-employed and could not work because of the outage, adding: "Never regretted more having my mobile and broadband on the same network."
The issues are also understood to have impacted some Vodafone shops.
The issues affecting Vodafone services have also impacted customers of other telecoms firms that use its network.
Downdetector saw a similar spike in reports on Monday afternoon from users of the mobile network Voxi, which is owned by Vodafone.
Lebara, which piggy-backs off Vodafone's network, has also been affected by the company's outage.
"Outages have been reported across multiple networks across broadband and mobile services," said Sabrina Hoque, telecoms expert at Uswitch.
These, she added, can be "a really frustrating experience for customers, especially when it's not clear how long it could last".
Vodafone has not yet said how long it expects its outage to last - though its website since appears to have come back online.
Cloudflare Radar, which tracks and displays patterns in global internet traffic, said in a post on Bluesky earlier it had "effectively dropped off the internet, with traffic dropping to zero".
The company has also not said what caused the issue affecting its networks.
"Incidents like this are often caused by a technical fault or configuration error rather than a major cyber-attack, so until more details are confirmed it's best not to speculate," said Daniel Card, a cyber expert with BCS, The Chartered Institute for IT.
"Having teams capable of diagnosing and responding rapidly to network failures is key to maintaining public trust and keeping the UK's digital infrastructure running smoothly."
Additional reporting by Ewan Somerville.
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