Former Prime Minister Mahathir Mohamad speaks during a press conference at his party headquarters in Petaling Jaya, Malaysia, Friday, May 29, 2020. Mahathir has been ousted from his Malay party in the latest twist to a power struggle with his successor Muhyiddin Yassin, but he has vowed to challenge it. (AP Photo)

KUALA LUMPUR, Malaysia - Malaysia's former prime minister, Mahathir Mohamad, was ousted from his ethnic Malay political party in the latest twist of a power struggle with his successor, but vowed Friday to challenge the move.

The 94-year-old Mahathir, along with his son and three other senior members, were expelled from the Bersatu party on Thursday for sitting with the opposition bloc during a brief Parliament session on May 18.

The party has has been split into two camps since intense political wrangling led Mahathir to resign as prime minister in February and the king to appoint fellow party member Muhyiddin Yassin as his replacement despite Mahathir's objection. Mahathir’s son, Mukhriz Mahathir, has since challenged Muhyiddin as party president with a vote that's been postponed by the coronavirus pandemic.

“Where you sit is not cause for sacking. ... I'm still the chairman (of this party)," a defiant Mahathir said at a news conference at Bersatu's headquarters. He went to the office with the four other expelled lawmakers Friday to challenge the party to sack them in person, saying their termination was invalid.

Mahathir co-founded Bersatu with Muhyiddin in 2016, and the party joined an alliance that won a stunning victory in 2018 polls, leading to the first change of government since independence.

The ruling alliance collapsed after Muhyiddin pulled Bersatu out to work with the former government party, which has been accused of massive corruption. Mahathir, a two-time prime minister, resigned in protest.

Mahathir has said he still has the support of a majority of lawmakers and has called for a no-confidence vote against Muhyiddin. The vote has been delayed amid the pandemic but could be held at the next sitting of Parliament in July.

“The unilateral action by Bersatu’s president to sack us without valid reason is due to his own fears in facing party elections as well as his unsafe position as the most unstable prime minister in the history of the country’s administration,” Mahathir and the four others said in a joint statement. They said they may take legal action to challenge their termination.

A party letter sent to the five said their membership had ceased but the letter was signed by a lower official who Mahathir’s group and others said had no power to remove them.

In a separate news conference at Bersatu’s office shortly after Mahathir left, party secretary-general Hamzah Zainuddin said Mahathir and the four others were not sacked but that their memberships were automatically nullified due to their own action against the party’s constitution.

“All eyes are on Mahathir’s next move," said Oh Ei Sun, a senior fellow at the Singapore Institute of International Affairs. “Muyhiddin would be gravely mistaken if he thinks this will slow down Mahathir’s relentless onslaught to not so much unseat him, but topple the present ruling coalition."

Muhyiddin had earlier tried to reconcile with Mahathir, but failed.

The current government includes the party of ex-Prime Minister Najib Razak, who is on trial on charges related to a massive financial scandal.

News from © The Associated Press, 2020