The Vietnamese health authorities said four travelers who arrived in the country a few days ago have showed flu-like symptoms, according to local media on Tuesday.

A 28-year-old man arriving at the Noi Bai airport from China's Hong Kong has higher body temperature. He is isolated and suspected of having the flu A/H1N1 virus.

Another suspected case was a 4-year-old child also arriving at the airport on Monday from Germany with high fever. The child was transferred to the National Institute of Infectious and Tropical Diseases for testing, said health officials in Hanoi.

According to health officials in Ho Chi Minh city, two children arriving in Vietnam from China's Taiwan on May 9 have unusually high temperature and are isolated in the No.1 Children's Hospital.

The test results of these above four suspected cases is not available now.

Vietnam has confirmed 19 cases out of the 23 suspected ones since the flu was declared to be epidemic of the 6-phase level by WHO, said health officials of Vietnam.

So far, there have been 74,271 travelers to Vietnam through the Tan Son Nhat International Airport, 7,365 of them from the epidemic-hit areas.

Vietnam's health officials had ordered relevant agencies to strengthen inspection at all border gates to ensure no possible appearance of the flu in Vietnam.