Malaysia’s 101-year-old former prime minister Mahathir Mohamad has been hospitalised for observation, his aide told AFP, following the death on Monday of his wife of seven decades.

The two-time prime minister was admitted to the National Heart Institute in Kuala Lumpur on Tuesday night, aide Sufi Yusoff said, though the reason for his hospitalisation was not immediately known pending an official diagnosis.

Sufi said Mahathir had not been getting enough rest following the passing of his wife, Siti Hasmah Mohamad Ali, on Monday and was feeling fatigued.

“He is in a stable condition,” Sufi told AFP in a WhatsApp message on Wednesday.

“He is exhausted from the emotional ups and downs, the hot weather and lack of rest. All of that is not a good combination for someone who is 101 years old,” he added.

His wife Siti Hasmah, who was a medical doctor and an advocate for public health, passed away at the age of 100. The couple raised seven children together.

Mahathir, visibly grief-stricken by her death, told the country’s former king through tears that he “didn’t expect her to die today”, in footage recorded at her funeral and posted on his official Instagram account.

Mahathir has suffered several heart problems in recent years and underwent bypass surgeries.

The centenarian has been hospitalised repeatedly in recent years, and most recently in January after suffering a hip fracture in a fall.

He has been dubbed the world’s oldest-serving leader after helming office twice, first holding the position as the Southeast Asian country’s fourth national leader from 1981 until 2003.

He then served as prime minister for a second time at the age of 92 from 2018 to 2020.