Oslo - Norway may seek foreign help to extinguish its biggest forest fire since World War Two, which has been raging for five days, the government said on Friday.

The Justice Ministry said it would check whether helicopters or special planes to drop water on the blaze were available across the Nordic region or elsewhere in the European Union, of which Norway is not a member.

"The idea is to check if anything is available, then possibly ask for assistance," a ministry spokeswoman said.

The fire has burned out about 5,000 acres, or 2,000 hectares, near the town of Arendal, about 260 km (160 miles) southwest of Oslo.

Norwegian media reported smoke had wafted as far as Denmark, some 120 km (75 miles) away across the Skagerrak strait.

The fire broke out after an unusually warm and sunny start to June. No lives have been lost but holiday houses have been destroyed and dozens of people evacuated.

Light showers were forecast for southern Norway on Friday but firefighter Ove Figstad told news agency NTB that "nothing short of a downpour will put an end to this".