A Vietnamese villager shows dead sea fish he collected on a beach in Thua Thien Hue province on April 21, 2016

Vietnam Thursday said it was investigating whether pollution is to blame for a spate of mysterious mass fish deaths along the country's central coast after huge amounts of marine life washed ashore in recent days.

Tonnes of fish, including rare species which live far offshore and in the deep, have been discovered on beaches along the country's central coastal provinces of Ha Tinh, Quang Tri, Quang Binh and Hue.

"We have never seen anything like it," aquaculture official Nhu Van Can told AFP Thursday.

The strange situation first came to light when farmed fish in the area began dying in great numbers, he said, with locals later discovering huge numbers of dead fish on beaches.

Local fishermen told state-run media that they are burying hundreds of kilograms of fish everyday.

"If you sail just three miles offshore, you can see dead fish all over the ocean floor," the state-run Tuoi Tre quoted local fishermen as saying.

Signs point to the fish having been poisoned by "unidentified substances," Tran Dinh Du, deputy director of agriculture in Quang Binh province, said, according to the report.

"We have asked people not to eat the fish and not use the fish as food for their livestock," Du added.

State news outlet Thanh Nien quoted worried locals saying they dared not eat any of the washed up fish, adding in their report that "all signs (are) pointing to an environmental disaster."

Tonnes of fish, including rare species, have been discovered on beaches along Vietnam's central coastal provinces

Central Ha Tinh province is home to a sprawling economic zone which houses numerous industrial plants, including a multi-billion dollar steel plant run by Taiwanese conglomerate Formosa.

Hanoi has dispatched teams of environmental experts and officials to investigate the phenomenon, the Ministry of Environment said in a statement posted online.

"We must quickly establish whether the fish have died because of environmental pollution," Environment Minister Tran Hong Ha said in the report.

Vietnam has a long coastline and much of the country's export income depends on seafood, including farmed shrimp, catfish and wild-caught tuna.

Last year, the country earned 6.6 billion dollars from seafood exports.

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© 2016 AFP