Authorities counted 108 new coronavirus infections over the past day.
Ninety-eight of them came among travellers returning from abroad, the National Health Commission said.
This is the highest number of reported infections since March 6, when authorities counted 143 cases.
The new infections take the official total to 82,160, as the 7th worst-hit nation in the world.
U.S., Spain, Italy, Germany, France, UK are ahead of China in confirmed cases, though the virus spread from there last December.
China is focusing its efforts on preventing a second wave of infections, especially among Chinese citizens returning from abroad.
Beijing on March 28 banned the entry of foreigners into China.
However, state media has reported that travellers crossing the border from Russia are spreading the coronavirus in the Chinese border city of Suifenhe in the north-eastern Heilongjiang province.
Around 300 cases of the coronavirus had been confirmed in the city by Saturday, including 100 infected people who did not appear to be showing any symptoms.
Of the new cases reported Monday, 10 were locally transmitted infections, including seven cases in Heilongjiang province and three cases in the southern Guangdong province.
The spike in locally transmitted infections comes after authorities had reported a string of days with no such new cases in late March.
A new cluster of infections is also feared in the southern metropolis of Guangzhou, in Guangdong province.
CNN reported on Sunday that the African community in Guangzhou was being targeted amid prevention efforts.
Africans in the city have reportedly been evicted from their homes and turned away from hotels even if they hadn’t travelled abroad recently.
The Chinese Foreign Ministry said in a statement late on Sunday that it expected local authorities in Guangzhou to “reject all racist and discriminatory remarks”.
China has so far reported 82,160 coronavirus cases including 3,341 deaths and 77,663 recovered patients.
While China had been the epicenter of the outbreak, the U.S. now has the most cases of COVID-19 in the world, with nearly 557,600 cases and more than 22,100 deaths. Globally, 1.86 million cases have been reported and almost 115,000 people have died.