Its main challenge is from the coalition led by opposition leader Anwar Ibrahim, who has campaigned on a promise to fight corruption in Southeast Asia's third-largest economy.

There were long lines at polling centres across the country despite concerns about monsoon rains, indicating a strong turnout from among the 21 million registered voters.

"I want a strong government and a stable economy so that there will be more job opportunities for the youth," Nurul Hazwani Firdon, a 20-year-old tutor, said as she went to cast her ballot in the rural town of Bera in Pahang state.

Malaysians face soaring food prices, and parts of the country are being battered by flash floods sparked by monsoon rains.

Najib's United Malays National Organisation (UMNO) usually dominates Malaysian politics but it suffered a humiliating defeat in the 2018 general election after a massive corruption scandal at state fund 1MDB.

The former prime minister, who was at the centre of the 1MDB storm, is currently serving a 12-year jail term.

Because of infighting in the two successive governments since 2018, UMNO crept back into power last year despite lingering corruption allegations, and is seeking a stronger mandate in Saturday's election -- called 10 months ahead of schedule.

Anwar's dream

The UMNO-dominated ruling Barisan National coalition is up against Anwar and his allies.

With age catching up, this may be Anwar's last chance to fulfil his long-standing dream of leading Malaysia.

"A win today would certainly be gratifying after more than two decades of fighting to win the hearts and minds of the people," Anwar, 75, told AFP before casting his vote in Penang state.

He added he was "cautiously confident" that his Pakatan Harapan (Alliance of Hope) could secure a simple majority in the 222-member parliament.

Caretaker Prime Minister Ismail Sabri Yaakob, from the ruling coalition, cast his vote in Bera.

"I hope the voters will choose a government that can guarantee security and stability," he told reporters.

A record 945 candidates are contesting for seats in parliament across the largely Muslim nation.

Former prime ministers Mahathir Mohamad, 97, and 75-year-old Muhyiddin Yassin head two other coalitions.

Corruption a key issue

Corruption was a key issue during the campaign, with opposition parties repeatedly warning that if UMNO wins, Najib could walk free and graft charges against other party leaders could be dropped.

The 1MDB scandal, in which billions of dollars in state funds were diverted to Beverly Hills properties, a superyacht, a Hollywood film and Najib's own bank account, sparked investigations in Singapore, Switzerland and the United States.

Analysts said there was no clear frontrunner among the four coalitions.

A survey by pollster Merdeka Centre on the eve of the elections showed Anwar's coalition winning 82 seats, and 33 percent favouring him as the prime minister.

Merdeka analyst Ibrahim Suffian told AFP it was "still possible for Anwar to achieve a simple majority" given the large turnouts in the final days of his campaign.

Malaysia lowered its voting age from 21 to 18 last year, a move that added six million voters to the rolls for this election.

Nearly 1.4 million of total registered voters are aged 18-20.

Analysts have said young voters lean towards the more progressive politics of the opposition.

The majority of registered voters, however, live in Malaysia's rural areas where the patronage politics dominated by UMNO still holds sway.

Analysts said the multi-racial country would be in for further political instability if no coalition wins a clear majority.

There is likely to be a "similarly fragmented political landscape after the election," Oh Ei Sun of the Pacific Research Center of Malaysia told AFP.