Taiwan on Tuesday slaughtered nearly 6,000 geese after 14 more farms were confirmed to have been infected in the latest outbreak of avian influenza that has led to the culling of more than 140,000 birds.

The confirmation brought to 21 the total number of farms infected by the outbreak since last week -- all in the south -- according to the Bureau of Animal and Plant Health Inspection and Quarantine.

The slaughter of the 5,830 geese at three farms in Chiayi county began late Monday night and was completed early Tuesday.

Further culls are expected as authorities adopt stringent measures to eliminate a new variant of the H5N2 and H5N8 strains, both discovered for the first time on the island.

"In order to swiftly wipe out the new disease, as long as the samples collected from any farm are confirmed as the H5 virus and the death rates there are high, all the poultry in the farm will be destroyed immediately," agriculture minister Chen Bao-ji told reporters.

"I can say for sure that within the next month the number of infected farms will keep growing."

More than 140,000 birds have been slaughtered since the first outbreak was confirmed at a chicken farm in Pingtung county, where 122,000 chickens were destroyed last week.

Taiwan has reported several outbreaks of H5N2 but has no recorded cases of the potentially deadly H5N1 strain, although authorities said pet birds smuggled from China tested positive for the strain in 2005 and 2012.