Former prime minister Dr Mahathir Mohamad is in stable condition after being admitted to the National Heart Institute's (IJN) Coronary Care Unit (CCU), according to his daughter Marina.

"He is now stable and responding well to treatment," she said in a brief statement this evening.

Marina said Mahathir had been undergoing treatment at IJN for the past two days.

On behalf of her mother Dr Siti Hasmah Mohd Ali and their family, she asked the public to pray for his recovery.

Earlier Mahathir received a visit from Prime Minister Ismail Sabri Yaakob, who in a brief social media post urged the nonagenarian's family to remain strong.

The Pejuang chairperson - who will turn 97 in July - was admitted to IJN for a full medical check-up and further observation last Dec 16 and spent a week before being discharged on Dec 23.

He was subsequently admitted to IJN for an elective procedure on Jan 7 and was discharged on Jan 13.