The O2 mobile phone network crashed tonight leaving thousands of customers across the country cut off. Users were left stranded, unable to make or receive calls or send texts, as the firm - which has 23 million customers in the UK - said it did not know when the problem would be fixed. Some customers also had no internet access. O2, Britain's second-largest mobile phone operator, admitted it was unclear exactly how many people had been affected. It said ‘thousands’ may be experiencing problems. The problems began this afternoon for some mobile users, the network said. O2 are urging customers to check their Twitter and Facebook feeds for updates - but the company’s webpage which displays live information about network coverage crashed. A spokeswoman said the problem was not 'location-specific'. ‘The problem is an issue within part of our core network that is preventing some mobile phones from successfully connecting,' she said. ‘The problem is not location-specific. All possible resources across our and our suppliers’ engineering teams are being deployed to restore service as soon as possible.’ Thousands of angry customers took to Twitter to complain. BBC television presenter Huw Edwards (@huwbbc), tweeted: ‘6 hours of non-service and counting, simply not good enough, O2.’ One Twitter user, Kelly Jones (@kelly-92), tweeted: ‘Having a phone that hardly works usually is annoying, but this whole no signal on o2 all afternoon is beyond irritating.’