A four-year-old child has become Vietnam's first victim of the H5N1 bird flu virus in more than a year, a health worker said on Tuesday, amid growing regional concerns about the virulent disease.

The death comes as neighbouring China scrambles to contain a new H7N9 strain that had not previously been transmitted from birds to humans but has now killed seven people since February.

"A test result confirmed the four-year-old boy was infected with H5N1," a staff member at the healthcare centre in Vietnam's southern province of Dong Thap, which handled the case, told AFP.

It was not immediately clear exactly when the child died and health officials in Hanoi were unavailable for comment.

It was Vietnam's first fatality from the H5N1 virus since late January 2012.

The boy, who was from a farming family, became unwell at the start of last week, the state-run Tuoi Tre newspaper reported.

After watching his grandmother kill a chicken, he developed a high fever and was admitted to hospital where he died, it said.

Hanoi last week banned all Chinese poultry imports and has stepped up border controls, including passenger temperature checks, in response to the new H7N9 strain in China.

According to the World Health Organization (WHO), Vietnam has recorded one of the highest numbers of fatalities from bird flu in Southeast Asia, with 62 human deaths since 2003, including two last year.

Neighbouring Cambodia is battling a recent unexplained spike in deaths from H5N1, which has killed eight people so far this year in the kingdom, including six children.

The H5N1 virus has killed more than 370 people around the world, according to the WHO, and scientists fear it could mutate into a form readily transmissible between humans.