Covid-19 measures will be tightened again from tomorrow to Aug 18, as Singapore goes back to phase two (heightened alert) to stem the recent spike in community cases.

Dining in will not be allowed during this period, among other restrictions, Trade and Industry Minister Gan Kim Yong said yesterday during a virtual press conference.

Maximum group sizes for social gatherings will be reduced from five to two. Indoor mask-off activities and classes at gyms and fitness studios will also cease.

Working from home will continue to be the default at workplaces, said the Ministry of Health, and safety measures calibrated according to vaccination status will be reintroduced "at an appropriate time".

The announcement by the multi-ministry task force tackling Covid-19 came as the number of community cases since the pandemic began peaked for the third straight day yesterday, with 182 locally transmitted cases. The increase was driven by the Jurong Fishery Port cluster which saw 142 more cases, taking its total to 321.

The latest tightening is aimed at buying time to reach the target of having two-thirds of the population fully vaccinated by National Day, said Health Minister Ong Ye Kung.

The task force co-chair acknowledged that the decision to revert to phase two (heightened alert) was "most unsettling" for the affected industries and the establishments.

"But we are so close, weeks away, to a stage where we have two-thirds or more of our population fully vaccinated around National Day, and then (we will be) able to much more decisively transit to a Covid-resilient posture.

"Therefore, now is really not the time to risk it all. So we need to bite this bullet, dial back on social activities, and use this time to push through the vaccination efforts."

The majority of local cases yesterday was again linked to the Jurong Fishery Port cluster, which has spread to 35 markets and food centres. The cluster linked to KTVs has 207 cases.

Mr Ong said that unlike the KTV cluster, which has spread among younger people, the wave of infection at the markets and food centres affects a much wider group of the population, including seniors.

The task force had to rethink its posture with the significant shift in the public health situation, he said. Key considerations include protecting hospital capacity from being overwhelmed.

The authorities also had to consider the level of community exposure, as well as about 200,000 people above the age of 60 who remain unvaccinated and therefore have a high likelihood of falling critically ill once infected, he said.

During this period of heightened alert, personalised services that require masks to be removed, such as facials, will not be allowed. Maximum event sizes will also be scaled down. Singapore last experienced similar restrictions from May to June, when community cases rose in part due to a cluster at Changi Airport.

On how the latest tightening fits into plans to live with an endemic Covid-19, Mr Gan said the authorities' direction has not changed.

"However, when we outlined our plans to live with Covid-19, we also emphasised that we needed to significantly raise our vaccinations, and... keep infections under control to protect the unvaccinated, especially the elderly."

A much bigger push will be made over the next few weeks to get seniors vaccinated, he said.

Calling the latest round of tightening a "very difficult decision to make", Finance Minister Lawrence Wong urged people to stay home, hunker down and minimise social interactions.

"We'll have these measures in place for a month, but we would review after two weeks and then consider adjustments to the measures based on the overall situation then," he said.

In a Facebook post yesterday, Prime Minister Lee Hsien Loong said: "We are all disappointed by this step back, but Covid-19 is a formidable foe. We have to feel our way forward, and be prepared for setbacks along the way."

The nation was making good progress in its vaccination efforts, he pointed out. "We are much safer now than six months ago. In four weeks' time, if all goes well, our vaccination coverage should be much higher, and we should be able to relax the measures," PM Lee said.

"We are not quite in the new normal yet, but steadily getting there."