By Jo Yong-hak

Taean, South Korea - South Korea deployed over 100 ships and thousands of troops on Sunday to clean up the worst oil spill in its history, which has blackened beaches, coated birds in tar and cast a foul smell over a nature reserve.

The slick has washed up in an area spanning 17km of the west coast, about 100km south-west of Seoul, that is home to popular tourist beaches, a national park and oyster beds. The spill is threatening to become a major environmental disaster.

The slick extends about 20km from the Hong Kong-registered tanker that began leaking an estimated 10 500 tons of crude oil on Friday, after a barge carrying a crane punched holes in its hull while it was anchored, the coast guard said.

"We have approximately 5 600 people who have been working from 5am on Sunday... doing all we can to prevent the situation from growing worse," said Ryu Hung of the Taean coast guard.

"Considering the tide, direction and velocity of the wind, the oil slick is not expected to expand further for now."

Volunteers and government personnel have been scooping up oil with buckets and absorbing cloth, treating birds covered in oil and scrubbing blackened rocks.

Ships deploying containment fences and oil skimmers have been trying to lessen the spill's impact. The largest slick was spreading in Mallipo Bay, a maritime ministry official said.

"The oil is about 10cm deep at Mallipo beach and we can't even see the sand underneath. There isn't even a single seagull nearby. They must have fled after the spill," said Lee Hee-yeol, a top village official in the region.

The government has declared several coastal counties to be in a disaster situation.

The leak is about a third the size of the 1989 Exxon Valdez spill of crude oil onto Alaskan shores, which was the costliest on record.

The clean-up alone from that disaster cost around $2.5-billion while the total costs, including fines and settlement of claims, were an estimated $9.5-billion.

The very large crude carrier (VLCC) Hebei Spirit was about five miles outside the port, waiting to unload its cargo of 260 000 tons of crude oil from the Middle East, when it was struck by the barge.