Japan on Monday ordered the slaughter of some 42,000 chickens as officials announced the country's second bird flu outbreak in less than a month.

DNA tests confirmed the H5 strain of the virus at a farm in the southwestern prefecture of Miyazaki after its owner reported Sunday that several chickens had died suddenly, the local government said.

Officials began the slaughter on Monday and asked farms within a 10 kilometre (6.2 mile) radius not to move their poultry outside of that area.

Later Monday, a poultry farm in Yamaguchi prefecture on the southwestern tip of Japan's main Honshu island said it had seen a higher than usual death rate among its chickens.

Initial tests showed a positive reading for bird flu, but more tests were needed for confirmation, the farm ministry said.

The confirmed case announced Monday comes about two weeks after the government ordered the slaughter of some 4,000 chickens at another poultry farm in Miyazaki—the first outbreak of bird flu at a Japanese poultry farm since April.

Local authorities locked down that farm and others nearby, with the movement of chickens banned while the area was sanitised.

Officials also set up stations to disinfect vehicles travelling on major roads near the affected farm to prevent the virus from spreading.

It is uncertain whether there is a link between the first outbreak and the second, a farm ministry official said Monday, adding that further testing of the strain would be conducted.

The second poultry farm is about 100 kilometres away from the site affected earlier this month.

Japan's agriculture ministry regularly warns farmers about the risk of infection, citing the continued spread of the disease in Asia, including in South Korea.