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.

Million 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.

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