Mahathir, who led the Southeast Asian nation for over two decades, has a long history of heart conditions and has undergone bypass surgeries, according to Reuters. In recent years, he has been hospitalised several times, most recently in October for a respiratory infection.
According to a statement from his office, he is currently under observation at the National Heart Institute in Kuala Lumpur. "He is resting, but we expect him to be back home by this evening," it said in a statement.
A physician who served as an MP until 2022, Mahathir reportedly drove himself to the event on Sunday, which also marked the 99th birthday of his wife, Hasmah Mohd Ali. Media reports noted that he cycled for an hour before showing signs of tiredness. His own birthday fell on Thursday.
Mahathir served as prime minister for 22 years until 2003. He returned to power in 2018 after leading the opposition to a historic victory, but his government collapsed less than two years later due to internal political conflict.