BEIJING: Mainland China reported 39 new coronavirus cases as of Sunday, up from 30 a day earlier, and the number of asymptomatic cases also surged as the government vowed tighter controls at land borders. The National Health Commission said on Monday that 78 new asymptomatic cases had been identified as of the end of Sunday, compared with 47 the day before.Hubei province, the original epicentre, accounted for almost half the new asymptomatic cases. A total of 705 people with asymptomatic cases were under medical observation around mainland China.The surge in asymptomatic cases, which China only began reporting last week, poses a worry as Hubei's capital Wuhan prepares to allow people to leave the city on April 8 for the first time since it was locked down in late January. One new locally transmitted infection was reported in the latest data, in the southern province of Guangdong , down from five a day earlier in the same province.