Malaysian Prime Minister Mahathir Mohamad submitted his resignation to the country's king on Monday, his office announced, a shock move that could plunge the country into political crisis.
The surprise announcement comes amid speculation that 94-year-old Mahathir was attempting to form a new ruling coalition that would exclude his promised successor Anwar Ibrahim.
It is not clear who will be the next Prime Minister or whether general elections will be held.
Mahathir's party, the Malaysian United Indigenous Party (Bersatu) announced Monday it would be dropping out of the ruling coalition Pakatan Harapan in support of the prime minister.
"All members of the House of Representatives of the party are also out of Pakatan Harapan. All of them have signed the Oath to continue to support and trust Tun Dr Mahathir Mohamad as the Prime Minister of Malaysia," according to a statement from Bersatu President Muhyiddin Yassin.
Deepening the political turmoil, Malaysia's Economic Affairs Minister Mohamed Azmin Ali and Housing and Local Government Minister Zuraida Kamaruddin were both fired from Anwar's People's Justice Party earlier Monday.
Nine other lawmakers declared their allegiance to the ousted pair and left the party as well, according to a statement from the lawmakers. The 11 lawmakers also announced that they are forming an independent block in parliament.
It follows meetings over the weekend between lawmakers of the ruling coalition and members of the former ruling party United Malays National Organization (UMNO), over alleged plans to form a new government, according to local news reports.
In response, Anwar called out "traitors" within his own party and accused members of Mahathir's party of plotting a change in the current ruling coalition.
"We know there are attempts to bring down PH and form a new government," Anwar said.
Speaking at his party headquarters Monday, Anwar said he had met with the Prime Minister and told him that, "this treachery could be dealt with together."
"Those from my party and outside are using his name. He reiterated what he said to me earlier. He had no part in it. He made it very clear in no way would he work with those in the past regime," Anwar said.
Confrontation had been building
Mahathir, the world's oldest leader, stunned many observers with a surprise election win in May 2018, ending six decades of dominance by the ruling UMNO-dominated Barisan Nasional coalition led by Najib Razak.
Entering into his second stint as prime minister, having previously held the position from 1981 to 2003, Mahathir was credited with turning Malaysia into a major trading and economic force in Southeast Asia.
After defeating Najib, who he blasted as corrupt and dictatorial, Mahathir had promised to hand over power to Anwar, who Mahathir himself once jailed.
Amrita Malhi, research fellow in the Coral Bell School of Asia Pacific Affairs at the Australian National University, said Mahathir's resignation "is likely a tactical move" with "no sure outcome."
"What tonight's situation shows is that after the intense jockeying of the last few days, the confrontation that has been building inside the Pakatan Harapan government since its election has now been triggered," Malhi said.
"Both parties and coalitions -- political formations that have existed for the last couple of years or decades -- are now splintering, and every single new grouping will have been preparing for any number of scenarios and contingencies in whatever negotiations are taking place now."
Mahathir and Anwar's complicated relationship goes back decades.
Anwar was the heir apparent to then-Prime Minister Mahathir until 1998, when he was fired and charged with corruption and sodomy. He spent six years in prison after being convicted of corruption charges in 1999 and of sodomy charges involving his wife's former driver in 2000.
Malaysia's highest court overturned the sodomy conviction and ordered him released from prison in 2004. However, the corruption verdict was never lifted, barring him from running for political posts until 2008.
In 2008, once his ban on political participation was lifted, Anwar was hit with further sodomy charges. He was convicted again and jailed in 2015. The government denied accusations that his imprisonment was politically motivated.
In 2018, Mahathir and Anwar put aside their longstanding rivalry to fight together to defeat Najib and his UMNO party, which forms the largest constituent in the Barisan Nasional coalition.
Following Mahathir's re-election, Anwar received a royal pardon that allowed him to enter politics again. Anwar's wife, Wan Azizah Wan Ismail, had endorsed Mahathir and served as his deputy in the coalition to oust Najib.
Speaking to CNN in 2018, she described the fraught relationship between her husband and Mahathir.
"We were great friends, then we were great enemies, and now we are together building our great country again. That is important. No feeling of revenge at all. We want to look forward to the future and build together."