Thousands have been evacuated from their homes

Five people died in the accident at the store, which was used to keep military weapons including rocket launchers.

Debris was thrown 10km (6 miles) by the blasts, which are still being heard 24 hours after the fire started.

The alert level was raised at the Zaporiz'ka plant 40km away and 10,000 resident have been evacuated.

But Ukraine's Prime Minister Viktor Yanukovych has given assurances that the incident poses no threat to the plant, the BBC's Helen Fawkes in Kiev reports.

Human error is being blamed for the accident in the Zaporizhzhya region, our correspondent says.

The prosecutor general's office accused officials from the defence ministry of negligence in ignoring warnings about the dangers of the arms dump. An investigation has been launched.

Satellite pictures of the scene show it looking like a war zone.

Witnesses say the explosions sent flames up to 300 metres into the air and showered surrounding villages with burning debris.

US aid request

Soon after the blaze started, there were several huge explosions which destroyed many buildings nearby.

The Zaporizhzhya nuclear power station is the biggest in Europe.

About 2,000 emergency workers are at the scene, but they cannot tackle the blaze properly until all the blasts have finished, officials say.

Ukraine's defence ministry said that special technology is needed and that Russia was sending experts to help.

Spokesman for the state gas monopoly Naftohaz Dmytro Marunych said a Grad missile hit a natural-gas pipeline in the area, cutting off all gas supplies to the nearby city of Melitopol.