East China's commercial hub of Shanghai has reached a milestone in its fight against COVID-19 with no new infections outside the quarantined areas for three days in a row.

After more than six weeks' efforts, the city has realized zero-COVID status at the community level in all its 16 districts, Zhao Dandan, deputy director of the municipal health commission, said at a press briefing on Tuesday.

It's a prerequisite for a gradual easing of restrictive measures and a major turning point for the megacity, which is home to over 24 million residents and had entered lockdowns since the end of March.

The city reported 77 symptomatic and 746 asymptomatic cases of COVID-19 on Monday. The first 31 patients tested positive during quarantine while the rest- 46 were previously asymptomatic. All the 746 asymptomatic infections were detected during quarantine.

According to the city's current three-tier disease control system, as of Monday, about 860,000 people still live under the strictest level of lockdown, which means home quarantine.

Meanwhile, residential compounds home to over 19 million people are designated as "prevention areas," which allow residents to venture out of their communities with certain rules attached. And another 3 million people are required to either stay at home or within their communities.

Return to normal in stages

Shanghai set out on Monday its clearest timetable yet for exiting a lockdown now in its seventh week, with the goal of restoring life to normal and fully restarting factories in June.

At a regular press briefing, Deputy Mayor Zong Ming said the city would reopen in stages, with movement curbs largely to remain in place until May 21 to prevent a rebound in infections.

The city began to reopen supermarkets, convenience stores and pharmacies from Monday, according to Zong.

Also from Monday, operators would gradually restore train services and domestic flights, she said. 

From May 22, bus services will gradually resume but people will have to show a negative COVID-19 test not older than 48 hours to take public transport.

"From June 1 to mid- and late June, under the premise of controlling the risks of a rebound in infections, we will make epidemic prevention and control a normalized routine, and fully restore normal production and life in the city," she said.

Zong said that authorities "remain sober" about the possibility of the outbreak rebounding, particularly as reports of new infections continue to come in from centralized isolation centers and older, rundown neighborhoods.

"Citywide, our prevention efforts are still not firmly enough established and it requires all of our continuing hard work and the cooperation of the broad masses of citizens and friends ... to restore the normal running of the city in an orderly fashion," she said.

The city is also ramping up its efforts to revive its infrastructure construction projects.

Zhu Jianhao, vice chairman of Shanghai Housing and Urban-Rural Construction Management Committee, said work has already resumed on 16 of the 24 prioritized major construction projects. These include the construction of a university campus, a green data center and a metro line. The remaining eight are in the preparatory phase, while a second list of prioritized projects is under review, Zhu said.

(With input from agencies)