South Korea is now declaring an area southeast of the capital a disaster zone because of a huge chemical spill in September.

About eight tonnes of hydrofluoric acid escaped from a chemical factory after an explosion in Gumi, 200 kilometres southeast of Seoul killed five workers and injured 18 others.

Since the Sept. 27 accident, more than 3,000 residents have sought medical help for rashes, as well as eye, throat and lung irritation caused by toxic fumes from the spill.

The prime minister's office said in a statement issued Monday that the area affected is a "special disaster zone," meaning Chung Un-chan's government will provide financial aid to cover recovery costs. Villagers in the zone will also be eligible for tax cuts and compensation.

The explosion and leak occurred as workers were unloading the acid from a tanker, officials said.

People in two rural villages near the scene of the accident say the fumes have damaged crops and made livestock ill.