Malaysia will hold a general election on May 9, the country's Election Commission (EC) said on Tuesday, in what could be the toughest test of the ruling-coalition's 61-year grip on power.

Embattled Prime Minister Najib Razak is under pressure to deliver an emphatic win for the Barisan Nasional (BN) coalition, as he struggles to appease Malaysians unhappy with rising costs and a multi-billion dollar scandal at a state fund he founded.

Najib ended months of speculation when he announced the dissolution of parliament last Friday.

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The 64-year-old Najib is expected to retain power, but analysts predict a tough fight from his old mentor and the country's most seasoned campaigner, former prime minister Mahathir Mohamad.

Mahathir, 92, transformed Malaysia into an industrial nation from a rural backwater during his iron-fisted 22-year rule until 2003. If elected, Mahathir would become the world's oldest prime minister.

"The EC has held a meeting and established that polls must be held within 60 days of the date of dissolution," the commission's chairman, Mohd Hashim Abdullah, told a news conference, adding that the election date was set for May 9.

Candidates would be nominated on April 28, meaning an 11-day campaign period. That falls short of the 15 days of campaigning in the 2013 election, and the minimum three weeks of campaigning period recommended by Malaysian electoral reform group Bersih.

It is also rare for the polling date to fall on a weekday, raising concerns of voter turnout.

"This raises the question for people wanting to take leave to travel to their hometowns and it reduces access to voters, unless 9 May is declared a public holiday," said Maria Chin Abdullah, former Bersih chairman who is now contesting elections with the opposition alliance.

The opposition has said previously that it expects the election to be unfair, after parliament recently approved plans to redraw electoral boundaries and pushed through an anti-fake news bill, changes critics say will favour Najib.

The government and the election commission has rejected these accusations. The commission said on Tuesday it had appointed 14 international observers and 14 local observers.

Najib has overseen a growing economy buoyed by a recovery in global crude oil prices and increased trade and infrastructure investment from Malaysia's largest trading partner, China.

But he has been plagued by reports of financial mismanagement at state fund 1Malaysia Development Berhad (1MDB), including that $681 million was deposited into his personal bank account.

Najib has denied any wrongdoing in connection with 1MDB, but the scandal created a rift between Najib and Mahathir, who has become the prime minister's harshest critic.