Malaysia's former Prime Minister Mahathir Mohamad was hospitalised on Thursday after suffering a "mild" heart attack, a hospital spokeswoman said.
Mahathir suffered a mild myocardial infarction and was admitted early this morning to the National Heart Institute in Kuala Lumpur.
The condition of the former premier is reported to be stable and the 81-year-old Mahathir is resting in a coronary care unit, reports said.
He had returned from New Zealand on Wednesday night.
Mahathir, a medical doctor by training, had a coronary artery bypass surgery in 1989.
"Dr Mahathir is advised to rest and thus, will only receive visits from immediate family members," the hospital said.
The former premier is expected to be kept under observation for one week, Bernama news agency said.
Mahathir has been in the news for a few months now over his relentless attack on Prime Minister Abdullah Badawi's administration.
The former premier has accused his successor, hand picked by him, of corruption and nepotism. His chief grouse has been the government's decision to scrap plans to build a new bridge to neighbouring Singapore.
Mahathir was prime minister for 22 years before stepping down in 2003.