HANOI – Hundreds of people have demonstrated in Vietnam against a Taiwanese firm they accuse of causing mass fish deaths along the country’s central coast, with some also blaming the government for a sluggish response to a major environmental disaster.

Though an official investigation has found no links between the fish deaths and a $US10.6 billion (about $A14 billion) coastal steel plant run by a unit of Taiwan’s Formosa Plastics, public anger against the company has not abated.

Hundreds gathered in Hanoi on Sunday holding banners that said, “Formosa destroying the environment is a crime” and “Who poisoned the central region’s waters?”

Others chanted, “Formosa out of Vietnam!” and took aim at the government for being aloof in what it now describes as one of its worst environmental disasters.

Demonstrations are rare in Vietnam and uniformed and plain-clothes police are usually quick to suppress them. On Sunday they cleared traffic to allow demonstrators to do a lap of a big lake in the heart of Hanoi.

Huge numbers of dead fish have appeared at farms and on beaches since April 6, impacting 200 km of coastline in four provinces, with no known cause.

The environment minister has demanded Hung Nghiep Formosa Ha Tinh dig up its waste pipe at the steel project to enable government to monitor its discharge.

The government’s initial probe found the cause may have been “red tide”, when algae blooms and produces toxins, or a release of toxic chemicals by humans.

Recently, public anger emerged when a comment by a Formosa official said Vietnam had to choose between catching fish and shrimp and building a modern steel industry.

“Here is Vietnam’s territory and there shall never be any case in which a Formosa steel plant has the right to tell the Vietnamese people to choose,” protester Cao Vinh Thinh said.

Several hundred protesters marched in Ho Chi Minh City, the economic hub, according to multiple accounts on Facebook, which is used by 30 million Vietnamese.

State-controlled media has not reported any of the demonstrations.

The government on Saturday ordered the trade and agriculture ministries to help buy seafood caught during deep-sea fishing.

– with Reuters