Dragan Jocic, Serbia's interior minister, said the blast shook the area around Baric, 30km southwest of the capital, on Monday.

Police sealed off the Prva Iskra factory, which produces explosives as well as toxic hydrofluoric acid, used as a component for household detergents.

Several ambulances went to the scene of the explosion where parts of the factory were ablaze.

The complex, censored repeatedly for emissions damaging to the surrounding environment, lies on the bank of the Sava river, which flows into the Danube at Belgrade.