Millions of voters in Malaysia are heading to the polls in an election that will see the country’s leader take on his 92-year-old former mentor.
Opposition leader Mahathir Mohamad will face off against PM Najib Razak’s ruling Barisan Nasional (BN) coalition.
Such an opposition victory would be unprecedented in Malaysia, where BN has ruled for 61 years, says a BBC report.
But critics have raised concerns the election will not be free and fair.
Malaysian politics has been dominated since independence by the BN coalition and its major party, the United Malays National Organisation (UMNO).
But this once powerful coalition has seen its popularity decline.
In the last election, in 2013, the opposition made unprecedented gains - winning the popular vote - but failed to win enough seats to form a government.
In a dramatic turn of events, then opposition leader Anwar Ibrahim was sentenced to five years jail on sodomy charges, which he claimed were part of a political smear campaign.
Mahathir, the country’s longest serving prime minister who was once an integral part of BN, and a mentor to Najib, abandoned the coalition in 2016. He now leads opposition coalition Pakatan Harapan.
As he left he declared he was "embarrassed" to be associated with a party "that is seen as supporting corruption".
Najib himself has been embroiled in a corruption scandal which saw him accused of pocketing some $700m from the 1Malaysian Development Berhad, a state investment fund.
He has vehemently denied all allegations and been cleared by Malaysian authorities.
The fund is still being investigated by several countries and Najib has been accused of stifling Malaysian investigations by removing key officials.
The government recently passed a law redrawing election boundaries, leading to accusations that it had gerrymandered constituencies to ensure they were filled by Malay Muslims, who are traditionally BN supporters.
In the days before the poll, election reform group Bersih 2.0 accused the Election Commission (EC) of multiple "electoral crimes" including irregularities in postal voting and failing to remove dead people from the electoral roll.
A controversial fake news law was also recently introduced, which critics say could be used by the authorities to muffle dissent.
Mahathir is himself being investigated under that law after alleging that his plane had been sabotaged.
The government has insisted the election will be free and fair, with Najib saying that the EC acted "for the good of all".
Voters will elect 222 members of parliament as well as state assembly members in 12 of the 13 states.
Malaysia uses a first-past-the-post electoral system, where the party that gets the most seats in parliament wins even if it does not win the popular vote.
