The Malaysian prime minister, 94-year-old Mahathir Mohamad, has submitted his resignation to the king.
Mr Mahathir’s shock resignation comes amid rumours that he may form a new coalition without his designated successor, Anwar Ibrahim.
The world’s oldest prime minister came into power in 2018.
In a shock victory, he ousted then-prime minister Najib Razak, who has been linked to a multibillion-dollar scandal involving a government fund.
The Prime Minister’s Office said the letter of resignation was submitted at 13:00 local time (05:00 GMT). No other details were included in the statement.
It is not clear who will be the next prime minister or if new elections will be called.
Mr Mahathir’s resignation followed a period of “intense political manoeuvring”, said the BBC’s South East Asia correspondent Jonathan Head.
Mr Mahathir has dominated Malaysian politics for decades – he was previously prime minister from 1981 to 2003, and was part of the long-ruling party Barisan Nasional (BN).
Mr Anwar was Mr Mahathir’s deputy but the relationship soured when Mr Anwar was sacked in 1998 after a leadership dispute.
He was later jailed on corruption and sodomy charges, which were widely regarded as politically motivated.
But in 2018, Mr Mahathir shocked the country when he announced that he was teaming up with Mr Anwar and joining the opposition alliance – Pakatan Harapan.
He said he was doing so to oust the government of Mr Najib, who had become embroiled in the 1MDB corruption scandal.
Mr Mahathir and Mr Anwar’s alliance won – and Mr Mahathir agreed to eventually hand power over to Anwar.
But Mr Mahathir repeatedly refused to say when he would transfer power – stoking tensions within the opposition alliance. (BBC News)