Some creditors of three subsidiaries of Indonesian coal miner PT Bumi Resources Tbk have applied to a Singapore court to overrule a moratorium granted to those units, in a move that could complicate their debt restructuring talks.

In May, the Singapore High Court gave Bumi Capital Pte Ltd, Bumi Investment Pte Ltd and Enercoal Resources Pte Ltd - which had issued a combined $1.375 billion in debt - until Oct. 24 to negotiate with creditors.

However, on July 6, "one 'ad hoc' committee of lenders applied to the court to 'set aside' the above moratorium," Bumi Resources said in a filing to the Jakarta stock exchange.

The hearing will be on Sept. 3, Bumi said. The company, which has numerous creditors worldwide, did not disclose the names of any creditors in the filing.

Bumi, part of the Bakrie Group, has been struggling to service its debt as its earnings have been hit by low coal prices.