Hong Kong health officials have warned of a significantly worsening Covid-19 outbreak in the Asian financial hub as suspected infection numbers rose in a congested residential area, Reuters reports.

Health officials said some 26 confirmed cases and more than 100 cases classed as preliminary positive were recorded in the last 24 hours, centred on three buildings in the Kwai Chung district north of the Kowloon peninsula.

"It's not easy for us to control the spread because we cannot trace all their whereabouts," senior Health Department official Dr Chuang Shuk-kwan said, referring to the 2,700 residents as well as workers and visitors linked to the building at the centre of the outbreak. She urged people across the city to limit their social engagements and avoid large gatherings.