The explosions that begun at 6.30am on July 3 2008 near Sofia were at Bulgarian army's unit 18 250 near the village of Chelopechene, east of Sofia, the Defence Ministry said in a statement. The blasts are expected to continue througout the day.

Four warehouses full of ammunition exploded, the Ministry said in the statement published on its website. The warehouses were full of cartridges with expired lifetime and conventional shells.

The statement did not specify the exact quantity of the ammunition, but according to Sofia mayor Boiko Borissov, who appeared on private broadcaster bTV hours after the incident, the warehouses had stored about 20 tons of ammunition. This is the reason why explosions are expected to continues through the day.

Focus news agency, however, quoted ministry data that said there were almost 1500 tons of ammunition in the warehouses.

"There is no danger for the population from leakage of noxious gases," the ministry's statement said. However, the ministry had one unit from the 38th regiment in Mousachevo for chemical protection on standby if necessary.

The ministry has dispatched several units to the area which is currently sealed by police. "Measurement of the air are taken constantly," the statement read.

The Ministry said that no one was harmed because of the incident, but ambulances and firefighters were ready to give any assistance.

Bulgaria's national medical coordination centre said, as quoted by Focus news agency, that anyone who was injured as a consequence of the blasts should call the centre's emergency hotline at 02/ 80 50 300.

Sofia airport, whose runways are close to the warehouses, will stay closed down until 2.30pm, Focus said.

The cabinet is holding an emergency meeting, at which it would decide on compensations to be paid out for damages incurred by the blasts.

A probe into the cause of the explosions was launched, but investigators are yet to enter the warehouses and will not do so until the explosions die out.