HANOI (AFP) - Vietnam said on Wednesday (Feb 22) it will punish 11 senior officials for misconduct over a toxic waste dump last year that killed tonnes of fish in one of the country's worst environmental disasters.

Taiwanese steel firm Formosa was blamed for the crisis that decimated livelihoods in coastal fishing communities in central Vietnam and was forced to pay US$500 million (S$700 million) in fines.

Fishermen and activists in authoritarian Vietnam have staged rare protests since the disaster and filed lawsuits demanding a fair share of compensation.

The 11 officials, who include a former environment minister and an ex-mayor, violated the law and mismanaged the crisis, according to a statement on the communist party's website.

"The violations... are serious and need to be considered and punished," the statement said, without clarifying what penalties would be handed down.

It said that environmental officials showed "a lack of responsibility in leadership, management and supervision," referring to the environmental assessment survey and the crisis aftermath.

Tonnes of dead fish, including rare species that live far offshore, washed up along the coast after the toxic waste dump, sparking public outcry in the communist country.

This month, a group of fishermen clashed with police in central Ha Tinh province as they tried to file lawsuits demanding compensation from Formosa.

The Taiwanese firm is no stranger to controversy in Vietnam, where anti-China riots at its Ha Tinh steel plant killed three in 2014.

The conglomerate has paid millions of dollars in fines over environmental mishaps elsewhere.