Bumi reported an operating loss for the first half compared to last year's profit as the miner was hit by falling coal prices.
The coal miner's operating loss came to $11m, down from a profit of $52 for the same period a year ago, reflecting a 20% fall in coal prices to $61.40 per tonne.
Earnings before interest, tax, depreciation and amortisation (EBITDA) declined to $74m from $139m.
The company said it has kicked off major cost reduction initiatives targeting all areas of the business, including corporate overheads.
Key areas of immediate focus are reducing contractor costs, Life of Mine (LoM) planning, exploration and evaluation activities, marine services, fuel management and marketing.
Despite lower coal prices, cash flow from operations increased by $6m to $189m primarily due to improved working capital management and lower costs.
Net debt fell to $389m at the end of the period, from $514 at the end of the month, following a review of capital structure to reduce interest costs and debt.
Production increased by 19% to 11.5m tonnes for the period, driven by output from its Indonesian subsidiary PT Berau.
PT Berau is on track to meet 23m tonnes of production for the year, with first half 2013 production up 19%, despite loss-time rain delays being 9% higher than planned.
In May, Bumi said it had lost $2.4bn before tax in 2012 as financial irregularities were discovered in PT Berau.
A review of PT Berau identified expenditure of $152m that had no "clear business purpose", which the auditors have recognised in the income statement as "other exceptional costs".
"There have been two areas of focus at PT Berau in the first half of 2013," said Chief Executive, Nick von Schirnding.
"One has been a major effort to address governance and financial control issues identified earlier this year. We carried out an extensive review of the financial position of Berau which has resulted in increased alignment with Bumi policies and procedures and the enhancement of our financial systems and controls. This process is ongoing and further improvements will be made during the year.
"The second is the development of a revised mine plan in conjunction with an asset optimisation exercise to profitably increase coal production, improve efficiencies and reduce costs."
He added that the company's plans to separate from the Bakrie Group and Bumi Resources were now "well advanced".
Bumi has agreed to sell its 29.2% interest in Bumi Resources to the Bakrie Group for $501m in cash.
Bumi and its wholly-owned subsidiary Vallar Investments UK have entered into a sale and purchase agreement with Long Haul Holding, a Bakrie-controlled entity, for the transaction.
Last month BT Borneo Lumbung Energi & Metal announced that affiliate,Ravenwood Pte, had agreed to acquire the Bakrie Group's 23.8% interest in Bumi.
The deal is conditional upon the sale of Bumi's 29.2% interest in Bumi Resources to the Bakrie Group.
The proposed sale will be put to Bumi shareholders and will require the approval of a majority of independent shareholders at a general meeting in autumn.
Meanwhile the company also announced the appointment of Paul Fenby as Chief Financial Officer and Keith Downham as Chief Mining Officer. They will be based in Jakarta when they join shortly.