Malaysia said it would restrict travel, ban public gatherings and order schools, universities and most shops to shut from Wednesday in a bid to control the spread of the coronavirus.
Prime Minister Muhyiddin Yassin said there would be a ban on Malaysians travelling overseas and on visitors entering the country under a restricted movement order imposed from March 18 to March 31.
Only shops selling essentials, including food stores and pharmacists, would be allowed to stay open, he said in a televised address.
Nearly two-thirds of Malaysia's 553 coronavirus cases have been linked to an Islamic gathering, making Malaysia Southeast Asia's worst-affected country and prompting a warning from the prime minister of "big news" on Monday to contain the epidemic.
Malaysia reported 125 new infections on Monday – its second biggest daily jump and most of them linked to the congregation of Islamic missionaries at a mosque in the capital, Kuala Lumpur, between Feb. 28 and March 1.
The event, attended by 16,000 people from several countries, was held at a time when Malaysia was in political chaos following the surprise resignation of its then prime minister.
Out of the 14,500 Malaysians who attended the event, only 7,000 have come forward for testing despite repeated pleas from government and religious officials, the health minister told a news conference.
The Kuala Lumpur gathering has also led to new infections in Singapore and Brunei. Singapore closed all mosques on Friday after five people who attended the Malaysia event tested positive for the coronavirus.
Announcing a US$230 million increase in the previously unveiled $4.7 billion stimulus package, Muhyiddin said he would make a big announcement later in the day, amid talks of a wider lockdown.
The chief cleric for the northern state of Perlis said it was a mistake for some of the missionaries who attended the Kuala Lumpur event to say it was God's will if they should become infected.
"For a virus that is easily transmitted such as this, aided by your active presence at mosques ... it is a serious wrong because you are endangering others in the community," Asri Zainul Abidin said, urging people to come forward and get tested.
The spike in cases in Malaysia, which until only just a week ago had a count at a little over 100, has stirred some anger towards the people who arranged the mosque gathering.
"What were the organizers thinking?" social media user Diyana Nasir asked on Twitter. "It's disappointing that they chose to proceed despite the growing pandemic."