Peabody Energy, the world's largest privately owned coal producer and the second biggest on earth, has filed for US bankruptcy protection.

The bankruptcy comes after a sharp fall in coal prices that left it unable to service a recent debt-fueled expansion into Australia, saying it is taking "a major step to strengthen liquidity and reduce debt amid an unprecedented industry downturn."

The company listed both assets and liabilities in the range of $10 billion (£7 billion) to $50 billion (£35 billion), according to a court filing.

Peabody's bankruptcy filing ranks among the largest in the commodities sector since energy and metals prices began to fall in the middle of 2014 as once fast-growing markets such as China and Brazil began to slow.