The Singaporean man and woman who died in a car crash in New Zealand on Thursday (May 4) were on vacation when the accident happened, the man's friend of more than 20 years has told The Straits Times.

Ms Rena Ong, 29, and Mr Chen Zhi Hao, 39, were married and had planned their vacation from as early as Chinese New Year this year (2017), Mr Chen's childhood friend Edmund Cheh told ST on Saturday (May 6).

"I missed the Chinese New Year gathering, but our friends said they talked about going to New Zealand for a holiday," said Mr Cheh.

The 39-year-old software developer first met Mr Chen when they were in Primary 3 at Changkat Primary School.

"From young, he showed leadership qualities and he loved football, especially the Blackburn Rovers," said Mr Cheh. "He was our football captain and we played as a group, when we were young. He loved to swim and was very adventurous and that's why he wanted to go to New Zealand, I think, he loved to travel."

Mr Cheh said he and his group of primary school friends were still in shock.

"He's a big brother to me," he said. "He took care of his family, took care of his friends, organised outings and chalet gatherings for us, and he was very loving to his wife."

Mr Cheh said the couple did not have any kids, and added that Mr Chen's family would fly his body back to Singapore on May 17. He did not know what the arrangements were for Ms Ong.

A colleague of Ms Ong and Mr Chen, who declined to be named, told ST on Saturday that he had just been in contact with Mr Chen a day before the fatal accident.

"We were just texting Zhi Hao on Wednesday," said the colleague, who works at a branch of the United States-based technology firm Crestron. "When we heard the news we just hoped they were kidding."

According to Ms Ong's Facebook profile, she had just celebrated her 29th birthday on April 26.

The pair worked at Crestron Singapore. Mr Stuart Craig, chief executive of Crestron Asia-Pacific, told ST on Friday (May 5) that the company was devastated at the loss.

The colleague told ST that Ms Ong and Mr Chen were "truly lovely people". He added that he did not know them very well personally, but they helped out a lot in work affairs.

According to their LinkedIn profiles, Mr Chen was a technical director and Ms Ong an operations executive at the company.

One of Ms Ong's secondary school classmates, who gave her name as Ms Nicole, said Ms Ong was a friendly, loving person.

They were classmates from Secondary One to Four at CHIJ Katong Convent, Ms Nicole told ST on Saturday.

"She was an easy-going friend, always there to help when she could," said the 29-year-old housewife.

Ms Ong and Mr Chen had been driving a rented camper van when their vehicle hit an oncoming car on State Highway 1, south of Dunsandel, New Zealand news site Stuff.co.nz reported on Friday.

A third person was taken to hospital with an arm injury.

The Ministry of Foreign Affairs is providing consular assistance to their families.