Scores of fishermen clashed with police Tuesday in central Vietnam as they tried to file lawsuits demanding compensation after a toxic waste dump by a Taiwanese firm killed tonnes of fish last year, activists said.

The mass fish deaths destroyed livelihoods in communities along the coast in central Vietnam where fishing is the main source of livelihood.

The Taiwanese firm behind the environmental disaster Formosa has paid $500 million to the government of Vietnam, some of which authorities started dispersing last year.

But the fishermen who tried to file suits Tuesday said they have yet to receive any compensation and are demanding payouts from Formosa.

Witnesses said they were stopped by police in central Nghe An province before clashing with police.

"A lot of police went there to stop them," Catholic priest Pham Xuan Ke, one of the leaders of the group, told AFP.

"Some people were beaten badly," he said, adding that many were hospitalised.

He said the local authorities agreed to receive the lawsuits, but officials in the area did not reply to an AFP request for comment.

Witnesses told AFP that several people were briefly detained after the clashes.

Photos on social media showed several people from the protest with bruises and bloodied faces.

Others showed crowds walking along the street with a banner reading "Help us sue Formosa".

A separate group of fishermen in September also tried to sue for greater compensation over the fish deaths, but their suits were dismissed by the court.

Tonnes of dead fish, including rare species that live far offshore, began washing up along Vietnam's central coastline in April.

Frustration at the authorities' perceived reluctance to tackle Formosa led to protests across the country, with police stepping in to arrest scores of demonstrators.