Rusal, the world's largest aluminium producer, on Monday reported a net loss of $439 million for the first half of 2013, citing falling prices, an excess global supply and economic uncertainty.

The Russian aluminium giant, which is listed in Hong Kong, also said revenue for the six months to June 30 fell 8.8 percent year on year to $5.2 billion.

"There is no doubt that the aluminium industry now faces a looming crisis of over-supply," chairman Matthias Warnig said in a statement filed to the the Hong Kong stock exchange.

"The problem of the excess stock cannot be addressed immediately, and the whole industry needs time to produce unconventional solutions to overcome this structural crisis and enter into a new phase of sustainable growth."

The net loss compared to a $1 million net profit in the first half of last year, and the company said it was partly related to a one-off sale of shares in its stake of Norilsk Nickel with the proceeds used for prepayment of debts.

Total aluminium output over the six months was 1,999 thousand tonnes, down 4.5 percent, as the company moved to reduce production.

Rusal said it now plans to reduce production by nine percent year on year, or 357,000 tonnes, in 2013 compared to a year earlier. This is 57,000 tonnes more than previously forecast.

The company said lower inflation forecasts and slower growth in China, as well as the expected wind-down of the US Federal Reserve's stimulus programme, was putting pressure on metal prices.

At the London Metal Exchange the average price of aluminium in the first half of the year dropped to $1,835 per tonne from $1,978 in 2012.

The company suffered a worse-than-expected loss of $337 million in 2012.