Acaica Mining's shares have plummeted as much as 18 per cent as the gold miner warned gold exports have been banned in Tanzania.
The surprise ban on gold and copper concentrate exports came from the Tanzanian ministry of energy and minerals following a directive ordered by the President.
"At this stage, Acacia has ceased exports of gold and copper concentrate and is urgently seeking further clarification from the ministry of energy and minerals," Acacia said in a statement.
"We will provide further updates as appropriate."
The FTSE 250-listed gold miner's share price rose ever so slightly in late afternoon trading to down 9.89 per cent at 480.3p.
Acacia Mining, formerly African Barrick Gold, describes itself as Tanzania's largest gold producer. In February, the firm announced it would more than double its annual dividend as it hit record production in 2016 while metals prices made their recovery. The firm is currently in merger talks with a Canadian rival Endeavour.