Teams of workers, aided by ships and aircraft, expected to complete on Monday the sea cleanup of 164,000 liters of oil that leaked off South Korea's southern coast, the coast guard said, after a pipeline run by GS Caltex Corp cracked at the weekend.

A cleanup of shore areas will take up to two weeks.

The crack and subsequent leak occurred on Friday at a quay off Yeosu, more than 300 km (185 miles) south of Seoul, while the 318,445 deadweight ton crude carrier Wu Yi San was preparing to berth and offload crude.

A 10-km (6.2-mile) stretch of coastline was affected by the incident.

"We're afraid of damage to fish farms in that area," Yeosu coastguard chief Kim Sang-Bae told reporters.

Oil remaining in the pipeline leaked, but none spilled from the tanker, which did not hit refinery production at GS Caltex, according to the refiner and the Korea Coast Guard.

The prime minister's office, in a statement issued on Sunday, said an oil boom to control the spillage would be expanded to a diameter of 9.5 km from 5 km, and 201 vessels and five planes would work on the clean up.

The coast guard official said the tanker was suspected of approaching the wharf at a higher than recommended speed, but the cause of the accident was under investigation.

He added that crude oil, naphtha and other oil compounds leaked from three cracked pipelines at the wharf.

The tanker is operated and managed by Singapore's Ocean Tankers, which said the vessel was under the control of two port pilots and assisted by five harbor tugs when it struck the shore jetty and pipeline.

Surveyors from ship safety classification society ABS and the ship's insurer, the North of England P&I Association, are helping the investigation and assessing damage to the ship, said Ng Kwang Chiau, senior vice president at Ocean Tankers' fleet management division.

He said the ship's voyage data recorder, or "black box", would be analyzed as part of the investigation. The company, he said, was co-operating with the probe and cleanup.

There were no injuries to the crew, Ng said. The front of the ship sustained minor damage, but the vessel was safely anchored.

The ship was chartered to Shell, Ng said, and talks would take place with the oil major about unloading options, he told Reuters.

South Korea's second-largest refiner, with a 775,000-barrels-per-day capacity, GS Caltex is equally owned by Chevron Corp, the second-largest US oil company, and South Korea's GS Energy, owned by GS Holdings .

In 2007, South Korea's worst oil spill occurred off the coast of Taean, when 10,500 metric tons spilled from a Hong Kong-registered tanker whose hull was punctured in a collision.

The spill devastated the region and triggered a number of suicides among local residents, as a legal wrangle over who was responsible and who qualified for compensation dragged on for years.

In November 2013, a small amount of oil leaked into the sea east of South Korea from a cracked pipeline run by the country's top refiner, SK Energy, owned by SK Innovation.

Reuters - AFP