SHANGHAI--Mainland China reported 99 new coronavirus infections on April 11, more than doubling from the previous day to reach a one-month high, as the number of single-day imported cases hit a record, official data released on Sunday showed.

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, according to China's National Health Commission (NHC).

Almost all the new infections--the biggest daily count since March 6--involve travelers from overseas. Just two out of the 99 cases were locally transmitted.

Shanghai, China's commercial hub, contribute to more than half of the imported cases. The city reported 52 new coronavirus cases on April 11, all involving Chinese nationals traveling from overseas, the municipal health commission said on Sunday.

Of Shanghai's new cases, 51 flew in on the same flight from Russia on April 10. The 52nd case involves a Chinese national arriving in Shanghai from a trip to Canada.

China's northeastern province of Heilongjiang reported 21 new imported cases on April 11, all involving Chinese nationals traveling from Russia.

The country's tally of infections now stands at 82,052, while the death toll stands at 3,339.