Cambodia ended on Thursday a blanket coronavirus lockdown in Phnom Penh after three weeks, as busy traffic returned to some streets of the capital, though authorities retained tighter curbs in some districts where infections have surged.

The Southeast Asian nation has recorded one of the world's smallest COVID-19 caseloads, but infections have climbed from about 500 in late February to 17,621 now, with 114 deaths.

Authorities recorded 650 new cases and 4 deaths on Thursday.

While health experts have warned about lifting curbs too quickly, the lockdown had triggered anger from some residents who called the distribution of food aid inadequate.

Authorities removed barricades on Wednesday night in "yellow" zones designated as safe for mobility, while "red" and "orange" zones with higher infection rates will remain under lockdown until May 12.

"I request that people should not be negligent, because we are living under a new way of life in the context of COVID-19," Phnom Penh's deputy governor Mean Chanyada told a news conference.

Yellow zones would see greater economic activity and traffic flows, but remain under a curfew from 8 p.m. to 3 a.m, he said.

As Phnom Penh opens up, authorities have also introduced new measures, such as only permitting 50 percent of workers in factories to return and with the priority on those vaccinated.

Other measure include more COVID-19 testing, higher vaccinations in parts of Phnom Penh with higher infection rates and a ban on alcohol sales.

The World Health Organization's (WHO) representative in Cambodia, Li Ailan, warned on Sunday against easing curbs too soon.

"Relaxing #COVID19 measures too fast and too soon means a possible surge," she said in a message on Twitter.