KUALA LUMPUR (Reuters) - Malaysian authorities are investigating opposition leader Mahathir Mohamad under an anti-fake news law over claims that his plane was sabotaged in the run up to a general election next week, police said on Wednesday.

Former Malaysian Prime Minister and candidate for opposition Alliance Of Hope, Mahathir Mohamad, shakes hands with his supporters after his nomination, on Langkawi island, Malaysia April 28, 2018. REUTERS/Lai Seng Sin

Malaysia is in the middle of intense campaigning for an election that pits Prime Minister Najib Razak against 92-year-old former premier Mahathir.

Najib’s government passed a law in April that criminalizes “fake news”, making it one of the first countries to do so. Critics have said the law is aimed at curbing dissent and free speech ahead of Malaysia’s May 9 election.

Mahathir, the opposition’s prime ministerial candidate, said last week that he suspected sabotage of a private plane that was to fly him from Kuala Lumpur to Langkawi, where he was to file his candidacy, after the pilot discovered some damage to the aircraft just before take-off.

The government ordered an investigation, following which the Civil Aviation Authority said the inquiry found no indication of sabotage. Its chairman had said it was wrong to make such “wild and false” claims for political gain.

Kuala Lumpur police chief Mazlan Lazim told Reuters on Wednesday that officers were investigating Mahathir after receiving a complaint.

“We have opened an inquiry based on a police report made against Mahathir,” Mazlan said.

A spokesman for Mahathir did not immediately respond to request for comment.

Under the anti-fake news law, offenders could be fined up to 500,000 ringgit ($127,000) and face a maximum of six years in jail.

Just this week, a Danish citizen was convicted for inaccurate criticism of police on social media, the first person to be prosecuted under the new law.

Najib is expected to win the election despite public anger over rising costs and a financial scandal at a state fund.

A survey by independent pollster Merdeka Center predicted that Mahathir’s opposition bloc is likely to win the popular vote, but Najib is expected to retain power through a parliamentary majority.

Under Malaysia’s first-past-the-post system, the party that gets the most seats in parliament wins even if it does not win the popular vote.

Critics say the odds have been stacked in the government’s favor because of gerrymandering through electoral boundary changes made by the Election Commission in March. The Election Commission and the government have said the move was free from political interference.