The men, aged 28-32, said they were staying at an apartment in District 4 to "look for jobs." They have now been put into a centralized quarantine zone as a Covid-19 prevention measure, the municipal police department confirmed.
They said they had entered Vietnam via a less-traveled path along the northern border with the help of smugglers, before traveling to HCMC on a bus.
Police were first alerted of the three through a local tip-off.
In the last two months, HCMC has discovered multiple incidents of people illegally entering Vietnam from China. Over 100 entrants have been found in the period, but the actual number could be much higher, police said.
As a coronavirus prevention measure, anyone wishing to enter Vietnam must undergo mandatory quarantine. Many seek to bypass quarantine through illegal entry.
HCMC raises coronavirus alerts on Tuesday after recording a new coronavirus-positive case: a 35-year-old man who went for a health check-up after displaying classic Covid symptoms like fever and coughing. If confirmed, the case would be the southern metropolis's second case in Vietnam's latest Covid-19 wave, which has seen 1,425 local cases in 28 cities and provinces since late last month.