ITV's online viewing service has been hit by problems during the opening match of the World Cup.
Football fans complained that ITV Player went down during the game between Brazil and Croatia tonight.
Responding to a barrage of criticism on Twitter, the service said on its feed: " We're seeing unprecedented numbers of users during the game.
"We apologise for any inconvenience, we're working hard to resume normal service."
Several users vented their frustration on the microblogging site.
Andrew Smith wrote: " Is everyone else's ITV Player down too? Get it sorted!"
Chris O'Callaghan said: " ITV player, why have you betrayed me?!"
Claire Kitson ?tweeted: " ITV Player congratulations on picking the worst time to do maintenance on your website! Would it have killed you to wait 15 minutes?"
An ITV spokeswoman said: "Due to unprecedented numbers of users during this game we are currently experiencing some technical problems with our live coverage via ITV Player on PC/Mac.
"We are working to resolve the issue as soon as possible and apologise for any inconvenience caused."
The broadcaster came under fire during the last World Cup in 2010 when more than a million viewers missed England's opening goal at the tournament in South Africa.
Viewers were left furious when ITV1 HD switched to an advert followed by a blank screen as Steven Gerrard scored in the fourth minute against the USA.