Image caption Reports say the leak has caused plants to wither in the affected area

South Korea has designated an area around a plant where an explosion led to a toxic chemical leak a special disaster zone.

Eight tonnes of hydrofluoric acid leaked from the Hube Global plant in Gumi after a blast on 27 September.

Five people died in the explosion. Since then some 3,000 residents have sought treatment for nausea and other ailments, Yonhap news agency says.

Three hundred people have moved out of the area, local reports say.

Hydrofluoric acid is corrosive and can cause burns to the eyes and skin. It can also irritate the respiratory system and is very toxic if swallowed.

The explosion and leak - which took place as workers unloaded acid from a tanker - have withered plants and trees in some areas and also affected livestock, Yonhap reports.

The government began a formal investigation on Friday, when many residents reported having been affected by the blast.

On Monday, officials designated the area a "special disaster zone", a statement from the prime minister's office said, meaning residents will be eligible for aid and compensation.

About 300 people from the villages of Bongsan-ri and Imcheon-ri have moved to temporary shelters amid concern over health risks.

Gumi is an industrial city about 200km (124 miles) south-east of Seoul.