Big companies such as Alcoa and Rio Tinto were closely watching a bout of political instability in Guinea on Monday, as KPMG warned miners to prepare for an era of increased geopolitical instability.

Reports of a military coup in Guinea raised fresh doubts over the West African nation’s ability to become a major iron ore producer to rival Australia after high commodity prices had revived hopes that Guinea could build a major iron ore province in the Simandou mountains.