Several hundred protesters disrupted a charity carnival organised by YMCA at Hong Lim Park on Saturday by marching through it, frightening special needs children performing on stage and confronting a minister present.

The rally's organiser, blogger Han Hui Hui, 22, had led the group - gathered to hear her speak about the CPF - around the park, together with blogger Roy Ngerng, 33, who is facing a defamation suit by Prime Minister Lee Hsien Loong.

The march began after Minister of State for Trade and Industry Teo Ser Luck arrived at the event for YMCA beneficiaries, attended by 900 people.

The marchers, several of whom waved Singapore flags, paused in front of the stage and chanted "Vote them out, PAP" and "Return our CPF" just as a group of special needs children was about to perform a dance item.

The reported heckling drew swift criticism from ministers and political watchers.

But the leaders of the rally defended their march, saying they did not heckle the special needs children on stage as many said they did.