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 has been admitted to hospital, a spokesperson says.

Mahathir was admitted to the cardiac care unit at the National Heart Institute, the spokesperson said on Saturday, but gave no details.

This is the second time the 96-year-old, who is still an active MP, has been admitted to the hospital this month. 

He was discharged after what was described as an successful elective medical procedure last week.

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

He was admitted and discharged in December after his doctors said they were satisfied with the results of necessary investigations.