The 45-year-old arrived at Sydney airport on Saturday with raw pork, quail, pate, squid and other food items, officials said.

It is the first time Australia has cancelled a visa over food under strict new bio-security laws aimed at keeping African swine fever out of the country.

The contagious disease has decimated pig numbers across Asia and Europe.

"In the midst of what is potentially the biggest animal disease event the world has seen, it beggars belief that someone would deliberately attempt to bring pork meat past our border," Agriculture Minister Bridget McKenzie said in a statement.

Under an amendment to Australia's Migration Act passed in April, visitor visas can be shortened or cancelled for bio-security contraventions.

On-the-spot fines can also be given to offenders, but authorities said that - given the scale of her offence - the unnamed woman was sent back to Vietnam instead and is banned from visiting Australia for three years.

Pork is big business in Australia - official figures estimate that the country's pork industry is worth more than five billion Australian dollars ($3.4bn; £2.6bn).

Australian bio-security agencies have stepped up screening efforts at airports and mail distributors in an effort to contain African swine fever. Concerns were raised after the disease was detected last month in East Timor, one of Australia's closest neighbours.

Ms McKenzie said that 27 tonnes of pork products have been seized at Australia's borders since February.

The minister noted a "concerning" increase in the number of these products contaminated with ASF, saying contamination rates jumped from 15% in February to 48% in September.

"That is why, if you are travelling from an African swine flu affected country, we are watching you," said Ms McKenzie.

Countries across Asia have been struggling to contain the spread of ASF, an incurable condition that is not dangerous to humans but is fatal to pigs. The disease has a mortality rate of up to 100%, according to the UN.

It emerged in East Africa in the early 1990s, moved through sub-Saharan Africa, and has also been recorded in Europe.

China - which is home to half the world's pigs, and where pork is often a staple food - confirmed an outbreak last August.

Since then, more than one million pigs have been culled in China, and over five million in Vietnam.

In South Korea hundreds of soldiers and civilian hunters have been deployed along the country's border with North Korea to kill wild boars and feral pigs to stop the spread of the disease.