China is stepping up scrutiny of inbound foreigners and tightening border control after the number of single-day imported coronavirus cases set a record, helping double the daily number of newly detected infections.

New confirmed cases in mainland China reached 99 on April 11 from 46 the previous day, with all but two involving travellers from abroad.

In addition, highlighting another major source of risk, newly reported asymptomatic coronavirus cases nearly doubled to 63 on April 11, from 34 the previous day.