A Malaysian court has convicted a Danish citizen over inaccurate criticism of police on social media, the first person to be prosecuted under a new law against fake news.

Salah Salem Saleh Sulaiman, 46, was charged with spreading false news after he posted a video on YouTube accusing police of taking 50 minutes to respond to distress calls after the shooting of a Palestinian lecturer on 21 April.

Police said they took eight minutes to respond to the shooting in the capital, Kuala Lumpur. The charge against Sulaiman said he had “with ill intent, published fake news through a video on YouTube”.

Sulaiman, who was not represented at the court hearing, pleaded guilty, but said the video was posted in a “moment of anger” and he did not mean any harm. “I agreed I made a mistake … I seriously apologise to everybody in Malaysia, not just in the Malaysian police,” said Sulaiman, a Danish citizen of Yemeni descent.

Malaysia is among the first few countries to bring in laws against fake news. The prime minister, Najib Razak, has been dogged by a multibillion-dollar corruption scandal involving an indebted state fund, and activists fear the new law could be used to criminalise opinions critical of the government. The country is holding a general election on 9 May.

Offenders could be fined up to 500,000 ringgit (£93,000) and jailed for up to six years.

The judge fined Sulaiman 10,000 ringgit but he opted to spend a month in jail because he could not pay.

Palestinian lecturer Fadi al-Batsh was shot dead by two men on 21 April. Police have yet to identify the suspects, but believe they are still in the country. Malaysia’s inspector-general of police, Mohamad Fuzi Harun, said a day after the shooting that their records showed a distress call was received at 6:41am and a patrol car arrived at the scene eight minutes later.

The Anti-Fake News Act covers “news, information, data and reports which is or are wholly or partly false” and included features, visuals and audio recordings.

The law covers digital publications and social media and also applies to offenders outside Malaysia, including foreigners, if Malaysia or a Malaysian citizen are affected.

A Malaysian media company filed a suit seeking to declare the law unconstitutional.

The US and several other countries are investigating allegations of cross-border embezzlement and money laundering at 1MDB, a state fund set up and previously led by Najib to promote economic development, but which accumulated billions in debt.

The US justice department says at least $4.5bn (£3.2bn) was stolen from 1MDB by associates of Najib, and it is working to seize $1.7bn taken from the fund to buy assets in the US, potentially its largest-ever asset seizure.

Najib, who denies any wrongdoing, has fired critics in his government and muzzled the media since the corruption scandal erupted three years ago.

Governments elsewhere in south-east Asia, including Singapore and the Philippines, have also proposed laws aimed at clamping down on the spread of fake news, to the dismay of media rights advocates.