Shanghai authorities doubled down on their offensive against Covid-19 on Friday, launching a new round of city-wide testing and warning residents their three-week lockdown would only be lifted in batches once transmission is stamped out.

The Shanghai government said on its official WeChat account, the city’s epidemic was showing a “positive trend” and that life in the city could return to normal soon as long as people stuck to strict rules to curb the spread of Covid-19.

And while some Shanghai districts tightened restrictions on movement, officials in neighbourhoods that met criteria for people to be allowed to leave their homes were still preventing them from doing so, fuelling anger and frustration among residents who have endured weeks of lockdown.

“Our goal is to achieve community zero-Covid as soon as possible,” the government said.

“This is an important indication that we win this major, hard battle against the epidemic ...so that we can restore normal production and life order.”

Shanghai locked virtually all of its 25 million people into their homes at the start of April after infections began to surge. Residents have faced income losses, difficulty getting food, family separations and poor conditions in quarantine.

Frustration with the rigid enforcement of draconian restrictions has reached new heights this week.

Health officials raised hopes for some return to normal by saying transmission had been curbed, only for city officials to pour cold water over such expectations as the highly-transmissible Omicron variant has proven hard to eliminate.

Late on Thursday, Shanghai announced a new round of “nine major” actions, including daily city-wide testing from Friday, accelerating transfers to quarantine centres, minimising people movement and ensuring enforcement of the rules.

The Chinese financial hub reported 15,698 new local asymptomatic coronavirus cases, down from 15,861 a day earlier.

New symptomatic cases stood at 1,931, down from 2,634.

There were 250 new cases outside quarantined areas, down from 441 the day before. There is particular focus on cases outside quarantined areas as those could be the first places where restrictions are relaxed, if Shanghai follows the pattern of other cities that have been under lockdown.

Eleven people infected with Covid-19 died in Shanghai on April 21, authorities said, taking the tally to 36 — all recorded in the past five days.

But there are doubts over the official toll, as many residents have said that a family member had died after catching Covid-19 since early March, but cases had not been included in official statistics.

The Shanghai government did not respond to questions regarding the death toll.

Businesses are beginning to reopen, though they have to operate under “closed loops,” which entail living on site, daily testing and rigorous disinfection.

Beijing last week published a list of 666 firms in Shanghai prioritised to reopen or keep operations going and the Shanghai government said on Friday 403 were doing so as of April 20, citing U.S. automaker Tesla (TSLA.O) as an example.

Economists and industry bodies caution, however, that factories face reduced trucking availability, fractured supply chains and a shortage of labour, and are far from resuming full production.