Malaysian Prime Minister Mahathir Mohamad has announced his resignation, paving the way for a possible formation of a new government.
Mahathir said in a two-line statement that he had informed the country's king of his resignation at 1pm Kuala Lumpur time (05:00 GMT) on Monday.
Mahathir's party, Parti Pribumi Bersatu Malaysia, has also quit the ruling government coalition, Pakatan Harapan (Alliance of Hope), according to the party president, Muhyiddin Yassin, casting doubt on the future of the partnership.
Mahathir's decision follows a weekend of political wrangling, after it was reported on Sunday night that his party was planning to form a new government that would exclude his anointed successor, Anwar Ibrahim.
On Sunday night allies of Mahathir, some renegade members of Anwar's People's Justice Party (PKR), and a slew of other Parliament members, including those from the opposition, UMNO, held talks in the outskirts of the capital, Kuala Lumpur.
The meeting fueled speculation of an impending collapse of the coalition government, and a political realignment with Mahathir remaining on top, with new coalition partners and Anwar's PKR out of the alliance.
The tussle between old rivals Mahathir, 94, and Anwar, 72, is the latest chapter in a long-running political saga between two of the country's most prominent political figures.
Anwar and Mahathir united ahead of the 2018 election to drive out the UMNO-dominated Barisan Nasional coalition that had ruled the Southeast Asian country for six decades in a surprise victory that led to the removal of then-Prime Minister Najib Razak.
Mahathir has also repeatedly promised to hand over power to his former foe.
But tensions between the two in their Pakatan Harapan alliance had been growing, as Mahathir resisted setting a specific timetable for keeping his promise to hand power to Anwar.
The coalition's political fortunes have been waning with defeat in five recent by-elections.
Anwar also had a split with party mate, Mohamed Azmin Ali, the econonic affairs minister, who was among those who joined the meeting on Sunday night. On Monday, Anwar's PKR announced the expulsion of Azmin as a member.
For his part, Azmin announced that he had quit Anwar's party, taking with him 10 renegade members of PKR, which until Monday was the dominant partner of the ruling coaltion.
At least 112 votes from members of the 222-seat parliament are necessary to form a new government.
Anwar was Mahathir's deputy when the latter was prime minister during his first stint from 1981 to 2003. But Mahathir sacked him in 1998 after they disagreed on how to handle the country's financial crisis.
Soon afterwards, Anwar was jailed for sodomy, charges he says were trumped up.