Former Malaysian PM Mahathir in hospital

Former Malaysian prime minister Mahathir Mohamad
Mahathir Mohamad was admitted to the cardiac care unit at the National Heart Institute -AP

Malaysia's former prime minister Mahathir Mohamad is in a stable condition after undergoing treatment at the National Heart Institute, his daughter says.

Marina Mahathir says her 96-year-old father was readmitted to hospital and had undergone two days of treatment following an elective medical procedure in early January.

"Siti Hasmah Mohd Ali (his wife) and family ask for the people to pray for his speedy and full recovery," Marina said on Saturday.

A spokesperson for Mahathir earlier said he was admitted to the cardiac care unit at the hospital but gave no details.

Mahathir, who is still an active MP, had been discharged from hospital after what was described as an successful elective medical procedure on January 8.

The National Heart Institute did not say at the time what procedure Mahathir, who has a history of heart problems, had undergone.

In December, he was admitted and discharged after his doctors said they were satisfied with the results of necessary investigations.