A Taiwanese company has been fined $9,000 for dumping waste water in a Vietnamese canal, an official said Tuesday, just months after another firm from the island was blamed for mass fish deaths in the country.

Public anger has mounted against foreign companies accused of polluting Vietnam since April when tonnes of dead fish washed up off the central coast in the country's worst ecological disaster in decades.

That incident was blamed on a Taiwanese steel firm called Formosa which was slapped with a $500 million fine for discharging toxic waste into the ocean.

In the latest case, authorities have accused Taiwan's Header Plan screw manufacturer of allowing contaminated water to run-off into the Moi canal in Dong Nai in southern Vietnam.

State media said residents have complained of increasing pollution in the canal since the plant opened in 2002.

The company has been ordered to clean up the waterway and fined more than $9,000, an official said Tuesday.

"The Header Plan Company must pay the fine according to an order from the Dong Nai People's Committee," said an official from the provincial environment department, speaking on condition of anonymity.

"We investigated the company's violation based on local residents' claims."

The official did not say when the waste water was discharged.

In June, Taiwan's Formosa agreed to pay the heavy fine for discharging contaminated waste which crippled livelihoods in the central coastal area where fishing is the main source of income.

Demonstrators held rare protests in the authoritarian country after the fish began washing up along shores near a Formosa construction site.

Protesters blamed officials for dragging their feet on investigations into the scandal, and many of the rallies were violently broken up with scores jailed.