A man holds a dead fish covered with crude oil spilled by the Hong Kong-registered tanker Hebei Spirit at Shinduri beach in Taean, about 170km southwest of Seoul. (AFP)

taean • South Korea's worst-ever oil spill spread along a pristine coastal area yesterday, fouling beaches and marine farms, as the government faced accusations it acted too slowly to limit the disaster.

Almost 9,000 troops, police and volunteers armed with shovels and buckets struggled to clean up the huge crude oil slick. Officials said it would deal a huge blow to tourism and oyster and abalone farms in the area.

The oil had hit 169 farms and 14 beaches as of yesterday evening and was still spreading south, said officials in Taean county 110 kilometres southwest of Seoul.

Some 140 ships and five planes were helping the clean-up but the Coast Guard said the slick has already hit 50 kilometres of coastline.

Park Myung-Jae, home affairs minister, said four townships would be declared a disaster zone, making them eligible for extra compensation.

Park vowed immediate aid of 5.9 billion won (6.4 million dollars) and said more state funds would be forthcoming soon.

But fishermen at Uihangri village, where 150 farms are located, were in shock. "It is a complete disaster," said oyster farmer Lee Nam-Kyu, 64.

Northwest winds were quickly pushing the slick south along the coast, said Lee Jae-Hak, of the Korea Ocean Research and Development Institute.

"Damage was bigger than expected because of wrong weather forecasts by the authorities," Lee said, adding that they failed fully to take seasonal winds into consideration after booms were set up.

Lee said it may take months or a year to remove oil from the land surface, "but it will take four or five years to remove chemicals and other pollutants."

About 10,500 tons of crude leaked into the Yellow Sea when a drifting barge carrying a construction crane smashed into an oil tanker on Friday.

The barge's cable to a tugboat had snapped during rough weather before it holed the 147,000-ton Hong Kong-registered Hebei Spirit in three places.