Farmers in Zambia have filed an $80bn (£58.5bn) lawsuit against two Chinese-linked firms, blaming them for an ecological catastrophe caused by the collapse of a dam that stored waste from copper mining.

Millions of litres of highly acidic material spilled into waterways in February, leading to mass fatalities among fish, making water undrinkable and destroying crops, the farmers said in court papers.

This is one of the biggest environmental lawsuits in Zambia's history, with the farmers saying the spillage affects about 300,000 households in the copper-mining region.

The US embassy issued a health alert in August, raising concerns of widespread contamination of water and soil in the area.

The lawsuit pits villagers, who are mostly subsistence farmers, against Sino Metals Leach Zambia and NFC Africa Mining, which are subsidiaries of Chinese state-owned firms.

A group of 176 of them have filed papers on behalf of their community in the High Court in Zambia's capital, Lusaka.

They alleged the collapse of the tailings dam - owned by Sino Metals Leach Zambia but located on the surface area of NFC Africa Mining - was caused by numerous factors, including engineering failures, construction flaws and operational mismanagement.

The firms have not yet commented on the lawsuit, but Sino Metals Leach Zambia has previously said there was a spillage of about 50,000 cubic metres.

The tailings release and breach was promptly brought under control within hours of detection, the firm said in a statement on 3 September.

In the court papers, the farmers stated they had only learned about the toxic nature of the water several days after the tailings dam collapsed.

This disaster has endangered the community's health, with reports of various illnesses, including blood in urine and chest tightness among residents.

Most villages had dug wells, but those too were polluted, and crops had to be burned for safety.

The petitioners are demanding that the firms deposit $80bn into a Zambian government-managed account for environmental reparation and full compensation, and they also propose a $20m emergency fund for immediate assistance and assessments post-disaster.

Last month, the US embassy ordered the withdrawal of its personnel from Kitwe - the largest city in the Copperbelt region - due to concerns regarding potential airborne contaminants from the spillage.

In response, Zambian government spokesperson Cornelius Mweetwa stated that there were no longer any serious implications for public health, asserting that there was no need to press the 'panic button' today to alarm the nation and the international community.