He called on Singaporeans to work with the government and not let down the guard, when he delivered his 2021 May Day Rally speech.
"It is not time to relax yet. This is a marathon. Let us keep jogging and keep ourselves safe," he said.
Lee reminded the Singaporeans not to make the mistakes some other countries have done, which were celebrating too early, relaxing too fast, letting the guard down, which caused another wave to come.
"If we have to do another lockdown like last year's Circuit Breaker, it would be a major setback for our people and for our economic recovery," Lee added.
Singapore was in the Covid-19 Circuit Breaker period from April 7 to June 1 last year, so as to stem the spread of the coronavirus.
The Circuit Breaker measures include home-based schooling and shutting most workplaces temporarily.
According to the Prime Minister, Singapore saw several new community clusters, some are quite big and worrying, emerged in the last few days, after a long period when it had few community cases.
A press release from the Ministry of Health on Saturday showed that the number of new cases in the community of Singapore has increased from 11 cases in the week before to 37 cases in the past week. - Xinhua