Malaysia’s long-time authoritarian leader Mahathir Mohamad is set to return as prime minister after leading an alliance of opposition parties to a shock election win.

The alliance led by 92-year-old Mr Mahathir’s Alliance of Hope party won a parliamentary majority Thursday morning (AEST) in a fiercely contested general election, ending the 60-year rule of the Malay-dominated National Front.

The result is a political earthquake for Muslim-majority Malaysia, sweeping aside the government of Prime Minister Najib Razak, whose reputation was tarnished by a corruption scandal and the imposition of an unpopular sales tax.

The opposition also made big gains in state elections including winning Johor state, where the dominant Malay party in the long-ruling National Front coalition was founded.

Mr Mahathir, in a televised address, said a representative of Malaysia’s constitutional monarchy had contacted the opposition to acknowledge its victory.

He added that a prime minister, expected to be him, would be sworn in within a day.

Mr Mahathir was credited with modernising Malaysia during his rule and pledged that the new government would not seek “revenge” against political opponents.

Malaysia enjoyed a feisty relationship with Australia during Mr Mahathir’s time in office — from 1981 to 2003 — often rebuking Canberra for its colonial past and role as America’s “deputy sheriff”, while stymying its efforts to join the Association of Southeast Asian Nations.

He notoriously snubbed the 1993 APEC summit in Australia, which led to anger and strained relations after then-prime minister Paul Keating labeled Mr Mahathir a ‘recalcitrant’.

Analysts said Thursday’s win by the opposition was a resounding rejection of the political status quo.

“This is a repudiation of Najib’s government from all walks of life from the very rural northern states to the more industrial southern coast,” said Bridget Welsh, a southeast Asia expert at John Cabot University in Rome.

Wan Azizah, the wife of jailed opposition leader Anwar Ibrahim, is expected to be sworn in as deputy prime minister.

Angered by the graft scandal, Mr Mahathir emerged from political retirement and joined the opposition in an attempt to oust Mr Najib, his former protege.

The US Justice Department says $US 4.5 billion was looted from state investment fund 1MBD by associates of Mr Najib between 2009 and 2014, including $US 700 million that landed in Mr Najib’s bank account. He has denied wrongdoing.

Analysts previously said the National Front might lose the popular vote but hold onto a majority in parliament due to an electoral system that gives more power to rural Malays, the party’s traditional supporters.

Faced with a reinvigorated opposition, the government used all the levers of power to further tilt the playing field in its favour, critics and analysts said.

Redrawn electoral boundaries were rushed through parliament last month, pushing likely opposition voters into districts that already support the opposition and dividing constituencies along racial lines.

A recently passed “fake news” law was an attempt to stifle debate and criticism, opponents said.

-with AAP