Authorities in Beijing have described new outbreaks in the Chinese capital as “very severe” and warned residents not to travel outside the city unless absolutely necessary. In a press conference reported by state media, city officials also said they had raised the virus risk level to their second-highest category and would, therefore, strengthen infection controls and reinstate lockdown measures. These have included reducing passenger numbers on buses and trains and sealing off the districts considered the highest risk.

In such districts, security checkpoints have been set up at the entrances to residential compounds, vehicle registrations are being recorded, while close contacts of people who test positive for the virus are now disallowed from leaving the city, the Beijing News reported.

Half of Beijing’s districts reported new coronavirus cases on Monday in the country’s most serious upsurge in infections for months. Authorities announced that 79 people had been hospitalized and there were 36 new infections in the Chinese capital, a day after more than 75,000 tests were conducted in the city of  20m.

The cluster of infections linked to Beijing’s largest seafood and vegetable market has become the most serious outbreak since China said it had largely succeeded in controlling the pandemic. Life in Beijing had mostly returned to normal after more than 50 days without a confirmed  case.