Organisers of This Is Tomorrow in Newcastle's Exhibition Park ended a set by band Foals early on Friday night because of safety concerns over a barrier near the front of the stage.
Saturday's acts featuring headliners Noel Gallagher's High Flying Birds is expected to go ahead as planned.
In a statement on Facebook the festival said: "Due to safety concerns with the front of stage barrier This Is Tomorrow Festival management made the decision to call an early finish to Foals set.
"This is entirely to protect the safety of the crowds and our audiences.
"The festival will take all necessary steps to remedy this situation for tomorrow’s (Saturday) event."
The band took to Twitter to apologise to fans but said there was nothing they could do.
They tweeted: "Newcastle we’re so gutted the show had to be pulled this evening. You were an amazing crowd & we were loving every second but it was deemed unsafe to continue. we’ll be back soon."
And drummer Jack Bevan added: "Such a shame. We were loving that but sadly there was nothing we could do.
"Thanks for being the best crowd while we were playing! Big big love xxx".
But fans have reacted angrily on social media and demanded refunds.
One said on Facebook: "We came from Belgium for the festival because we are huge Foals fans, we will never come to another festival in Newcastle that’s for sure!
"We hope you are thinking about at least partial refunds for those with day tickets."
Another posted: "We came specifically to see Foals and booked well in advance. We should be eligible for some kind of refund since the organisers couldn't put on the event that was advertised."
And another said: "Foals were cut massively short leaving the fans very disappointed."
The event runs until Sunday when Welsh rock band The Stereophonics due to bring the curtain down.