UPDATED 3.48PM | Dr Mahathir Mohamad has also resigned as Bersatu chairperson, an hour after party president Muhyiddin Yassin announced that Bersatu quit Pakatan Harapan.
Earlier, Mahathir also submitted his resignation as the prime minister to the palace.
His resignation comes amid political manoeuvring to form a new coalition comprising former PKR leaders aligned to Gombak MP Azmin Ali, Bersatu, BN, PAS, GPS and Warisan.
Mahathir provided no reasons for his resignation as both the prime minister or as Bersatu chairperson.
His exit as the Bersatu chair fuels speculation that he could be at odds with Muhyiddin and others.
Meanwhile, The Edge quoted sources as claiming that Mahathir resigned from the party he founded because is against working with Umno.
Bersatu has 26 parliament seats.
Meanwhile, former PKR deputy president Azmin Ali said he and 10 other MPS would form an independent block.
A number of top leaders from Umno, PAS and Bersatu congregated at a hotel in Petaling Jaya last night, along with Azmin and other PKR MPs aligned to him.
This fuelled speculation of a move to form a backdoor government.
Following Mahathir’s resignation as prime minister earlier, sources offered two different scenarios for Mahathir's decision.
One source claimed the 94-year-old premier was fed-up with what transpired in the last 24 hours as he was purportedly against the move.
Whereas, a second source alleged Mahathir is resigning as the Pakatan Harapan prime minister in order for him to become the legitimate prime minister of the new coalition.