World-renowned liver transplant surgeon Tan Kai Chah, who performed a life-saving liver transplant on former actress Andrea De Cruz, died yesterday morning on the island of Hainan.

The 68-year-old Malaysian, popularly known as Dr K.C. Tan, is believed to have died of a heart attack.

He had been on a business trip, running the Asia Advance Multi-Specialty Medical Centre - the first Singapore-operated medical centre on the island in southern China, said the Asian American Medical Group yesterday evening.

Dr Tan was the executive chairman of the Singapore-based medical group, which includes the Asian American Liver Centre - a clinic in Gleneagles Hospital - where he practised.

Ms Angela Choong, its group chief financial controller, said Dr Tan had sent his usual "good morning" greetings to her and other colleagues hours before he died between 8.30am and 9.30am in his hotel room.

"His death was very sudden and the team is still coming to grips with it. Dr Tan was a good boss who was very well-respected in his profession. He cared immensely for his patients and worked tirelessly to give them the best care," said Ms Choong.

Dr Tan leaves his wife and daughter.

He was well-known as the surgeon who performed a liver transplant on Ms De Cruz - local actor Pierre Png's wife - who had liver failure and almost died after taking dubious slimming pills in 2002.

Mr Png, her then boyfriend, donated part of his liver to save her. It was the first liver transplant where the Ministry of Health allowed non-related living donors to donate.

In an Instagram story yesterday evening, Ms De Cruz wrote: "Rest in peace KC... thank you for the last 19 years. I miss you already..."

Mr Png also posted a tribute on his Instagram page: "Many continue to praise me for what I did, but I always say it was all you KC... Today we lost a great man, a pioneer in liver transplant surgery."

Dr Tan also treated Johor Sultan Ibrahim Iskandar's son, who died of liver cancer in 2015 - also on Dec 5.

In a Facebook post, Sultan Ibrahim wrote: "Dato' Dr K.C. Tan headed the team of the Singapore doctors who looked after and treated my late son, Almarhum Tunku Abdul Jalil, Tunku Laksamana of Johor. It is a strange coincidence that he passed away today, on the same day that Jalil left us. May Dr K.C. Tan rest in peace."

Dr Tan was renowned for his pioneering work in living donor liver transplants (LDLT).

He pioneered the living donor liver transplantation programme in Singapore, and helped to start a similar programme at the King's College Hospital in London.

In 1995, he performed South-east Asia's first paediatric LDLT in Kuala Lumpur.

In April 2002, the first successful LDLT in adults in South-east Asia was performed at Gleneagles Hospital.