The organisers of a Singapore Day carnival in Australia have drawn flak for allegedly turning away non-Singaporeans.

Some Australians complained about being barred from the event, according to a report in the Australian newspaper The Telegraph on Tuesday.

The event at the Royal Botanic Gardens, held on October 12 in Sydney for the first time, was organised by the Overseas Singaporean Unit under the Prime Minister's Office with the aim of keeping Singaporeans living abroad connected to their home country.

According to the event's website, Singapore Day is exclusively for Singaporeans and their families. To gain entry, people must also pre-register and bring along their electronic ticket.

But an Australian man called into a radio station 2GB to complain that he and his father had been turned away because "they were not Singaporean", raising questions of discrimination.

Royal Botanic Gardens acting executive director Brett Summerell was quoted by the Telegraph as saying that there was some "community concern" over the situation.

"My understanding was it was a private event and they paid a fee to hire out the area," he said.

"We had initial concerns over people not being let in but they had told us people would only be turned away if it reached full capacity or they didn't pre-register online."

In its sixth edition since 2007, this year's Singapore Day attracted more than 6,000 Singaporeans and featured local fare such as satay and chicken rice, and music and displays.

It was also attended by Deputy Prime Minister Teo Chee Hean and Minister in the Prime Minister's Office Grace Fu.