Chile ordered strict new quarantine measures on three districts in the capital Santiago after a sudden spike in coronavirus cases Sunday.
The Health Ministry reported a surge of 1,228 new infections, bringing the total to nearly 20,000 nationwide and dealing a blow to hopes it was over the worst of the crisis.
"If we do not win the battle in Santiago, we can lose the war against the coronavirus," warned Health Minister Jaime Manalich.
Cerillos, Quilicura and Recoleta districts – as well as the northern mining city of Antofagasta – would be quarantined from next Tuesday, he said.
Santiago, with a population of seven million, has been the country's main center of infections, particularly in its three richest suburbs.
However, the virus began to spread in the city's more densely populated areas over the past couple of weeks.
The setback follows criticism of the reopening of some commercial streets in Santiago after the government last week outlined "a return plan" for the economy.
The ministry reported 13 new deaths Sunday, all in the metropolitan area, bringing the total to 260.
Chile has Latin America's highest rate of coronavirus testing – 14,000 a day and nearly 200,000 overall according to officials – and had on Thursday cautiously celebrated evidence infections had peaked.
It was among the first countries to explore the idea of an "immunity passport" for recovered Covid-19 patients to allow people back to work.
However, it dropped the measure after the World Health Organization warned there was no certainty the disease could not strike a person twice.
Instead, Chile will provide "discharge cards" to some 10,000 recovered patients.
Manalich said these would be delivered in the next few days and would be valid for three months "until there is scientific evidence" on virus immunity.
The cards will enable holders to move freely in quarantined areas and to rejoin the workforce.
The government responded quickly to the first cases on March 3, introducing a nationwide curfew and selective quarantines on areas with high incidences of the virus.
Schools, universities and businesses were closed as part of social distancing measures and transport restricted.