"It appears to be so. I have been informed that he is now in the intensive care unit at the Langkawi hospital," Mokhzani Mahathir told AFP.

"It is unfortunate that it had to happen," said Mokhzani. The 81-year-old former prime minister was admitted to hospital at 4.00 pm local time yesterday, according the Star daily's news alert service. His condition was reportedly stable.

A local lawmaker from Mahathir's homestate of Kedah told AFP on condition of anonymity that he had visited the former premier at the hospital.

"Tun is conscious, he is alert, there is nothing to worry about and he is accompanied by his wife (Siti Hasmah Mohamed Ali)," he said, referring to Mahathir by his honorific.

News of him being hospitalised spread rapidly in this tiny resort island, which led to Mahathir's friends crowding the hospital floor where he was admitted.

Scores of supporters also turned up at the hospital grounds.

Mahathir suffered a mild stroke in November last year, caused by a clot that restricted blood flow in one of his arteries, but subsequently recovered.

The heart attack was blamed on "excessive travelling" after he had visited Saudi Arabia and New Zealand.

He also suffered a heart attack in 1989 and had bypass surgery.

Mahathir retired from office in 2003 after 22 years in power, handing over the reins to Abdullah Ahmad Badawi, whom he has since accused of nepotism and corruption -- charges the incumbent leader has repeatedly denied.

Abdullah and his Singaporean counterpart, Lee Hsien Loong, arrived in Langkawi on Monday for informal talks aimed to enhance ties.