AceShowbiz -

Rihanna displeased her fans when she recently performed at Singapore Grand Prix concert. Fans admitted to being disappointed as they claimed that the 25-year-old Bajan singer didn't really sing on the stage.

Some angry fans blasted Rihanna on Twitter, accusing her of lip-syncing and being drunk or high on drugs. "Rihanna looked ratchet as hell, she can't dance and I swear she looks drunk or high on some drugs on stage the whole time," a Twitter user wrote.

"Lol at folks in Singapore surprised that Rihanna was high & lip-syncing at her show! #duh #overrated," another fans tweeted. Another added, "I'm disappointed for those who paid 26K for Rihanna's Concert because the girl was lip-syncing. Not worth the penny. Huhu."

One eagle-eyed male fan spotted that Rihanna's microphone wasn't even on. He tweeted, "SPOILER ALERT: Rihanna is lip-synching. From the ex-soundman next to me. Plus red light isn't on on her mike. She walks like Rihanna though."

It's not the first time Rihanna has been accused of lip-syncing. Last July, promoters of Scotland's Tea in the Park festival defended the ex-girlfriend of Chris Brown's choice to fake her performance, saying, "I wouldn't be able to sing like that if I was bouncing up and down and dancing."