Guns N' Roses concertgoers have flooded the Facebook page of LAMC Productions with complaints after the rock band's sell- out concert last Saturday at Changi Exhibition Centre.

According to concert promoter LAMC, the event is one of the biggest rock shows held in Singapore, with close to 50,000 tickets sold.

But music fans have taken to its Facebook account to slam it for its poor organisation of the event. The main grouse appears to be about a cashless payment system for buying food and drinks at the event.

Audience members said they had bought credits in advance, which were stored in an RFID tag, but could not use them as the food and drinks ran out.

LAMC has apologised in a Facebook post and promised to refund unspent credits. "LAMC would like to add that we are apologetic to attendees who were unable to spend their full RFID credits," it wrote. "Our wish is for our audience to be fulfilled; we therefore pledge to refund the unspent RFID credits. We are working hard with our teams to formulate a refund process."

But the complaints continued to come.

A Facebook user known as Tim Weiss wrote in a comment that was liked more than 100 times: "Your organisation of this show was an absolute disgrace. It was completely amateur and was a complete disappointment to thousands of people, many of whom travelled from abroad. I will never attend another event promoted by LAMC. Absolutely horrible."

Concertgoers also seemed unhappy about long queues for food, drink and merchandise, and the shuttle bus arrangements.

"I had to miss parts of the concert just for all this lining up," wrote Melinda Wong, who said she queued for two hours.

Another angry commenter said she queued two hours for beer only to find that her RFID tag was not topped up, although she paid concert staff $50.

People also asked the organisers why tickets, which most paid hundreds for, were not checked at entry.

"I did not show anyone my ticket. This is incredible. Anyone could have gone in for free, they just let the people in..." wrote Alex Ballesteros in a message to The Straits Times.

He queued for 80 minutes for food and drink, only to be told that both had run out, he said.

The shuttle-bus services, which concertgoers had to pay for, were inadequate and the wait was about two hours, they said.

VIP ticket-holders also complained about the location and size of the VIP pen.

Concert tickets were priced from $199, with VIP packages costing up to $2,063. Shuttle-bus passes were sold at $15.

When contacted, LAMC referred to its Facebook statement on the matter and declined further comment.