Singapore has moved to extend restrictions to combat coronavirus until early June, as the number of cases in the city state exceeded 9,000 due to a growing number of infections in its crowded migrant worker dormitories.

While Singapore had drawn worldwide attention for what was seen as its success in containing the early stages of the outbreak, a new and quickly expanding second peak of infections has underlined how easily the virus is able to return.

The tiny city-state has the highest number of cases in south-east Asia, a huge increase from 200 infections on 15 March, when its outbreak appeared to be nearly under control. About 3,000 cases have been reported in the past three days.

As countries around the world have begun deliberations about loosening their own restrictions, health authorities in the city reported 1,111 new cases on Tuesday, taking the total to 9,125, with the vast majority of new infections in foreign worker dormitories, which have become the centre of the city’s outbreak.

The latest tally of infections follows Monday’s count of more than 1,400 new cases.

The prime minister, Lee Hsien Loong, said restrictions – which include closures of businesses and schools, and asking people to stay home – would be extended to 1 June. They were imposed at the start of April and had originally been due to end on 4 May.

“Many will be disappointed by the extension,” said Lee in a televised address, acknowledging that businesses and workers were “hurting greatly”.

“But I hope you understand that this short-term pain is to stamp out the virus, protect the health and safety of our loved ones, and allow us to revive our economy.”

Authorities also said that restrictions would be tightened, with the number of people still working in services deemed essential to be reduced, and people asked to exercise outside alone.

The first infection among Singapore’s migrant workers occurred in February, when a 39-year-old Bangladeshi national, known as “Patient 42”, developed symptoms of the coronavirus.

While 19 other people who had come in contact with him were traced and tested, it appears Singapore was slow to test for the disease in the crowded dormitories leading to a cluster emerging in the Seletar Aerospace Heights construction site, where they were working to expand aerospace manufacturer Bombardier Aviation’s facilities.

Estimates suggests that up to a third of infections in Singapore are Bangladeshi workers. “I am afraid 1,200 to 1,300 Bangladeshis have been infected so far,” Mustafizur Rahman, Bangladesh high commissioner to Singapore, told the Dhaka Tribune last week.

In a bid to reduce the chances of infection, thousands of workers have been moved to alternative accommodation such as vacant apartment blocks, while several dorms have been quarantined.

Despite the surge in the number of cases among migrant workers, numbers among Singaporean nationals remain under control.

The death toll from the virus stands at 11.

Low-wage migrant workers, a vital part of Singapore’s workforce, account for at least 60% of its infections.

More than 200,000 workers from Bangladesh, India and other poorer Asian countries live in tightly packed dormitories. Clusters of infections have expanded rapidly in the dorms after they were overlooked in the government’s earlier health measures.

Social distancing is impossible in the dormitories, which house up to 20 men per room with a shared kitchen, toilets and other facilities. Most work in construction, shipping and maintenance jobs.

More than half of the 43 registered dormitories have reported active viral clusters. At least 18 of the dormitories were declared isolation areas where workers have been quarantined. Several thousand other workers have been moved to other locations to reduce crowding.

The government expects the number of cases to rise further as testing at the dorms continues, but hopes that the country’s partial lockdown, mandatory wearing of masks and strict social distancing will help curb the spread of the virus.

The country’s national development minister, Lawrence Wong, said said in a Facebook post there was evidence that transmission across multiple dormitories could have occurred at construction sites or at places where the workers congregate on their days off to shop and socialise.