South Korea, the world's fifth-largest crude oil importer, shipped in 1.56 million tonnes of U.S. crude oil in November, or 382,357 barrels per day (bpd), according to the customs data. That was up 80.4% from 867,687 tonnes a year earlier, but down 12.9% from nearly 1.8 million tonnes in October.

The United States was South Korea's No.4 crude oil supplier in November after Saudi Arabia, Kuwait and Iraq.

"November South Korea's U.S. crude volume was actually steady to October," Emma Li, senior oil analyst with Refinitiv.

But Li said, a rise in freight rates in October, which affected November-loading vessels, would weigh on January and February arrivals.

Freight rates surged in October amid a tanker shortage following U.S. sanctions against Chinese shipper COSCO over alleged Iranian oil cargoes.

South Korea has imported over 1 million tonnes of U.S. crude oil every month this year, hitting the highest monthly intake of 1.91 million tonnes in July, or 450,838 bpd, the data showed.

South Korea's U.S. crude imports were 16.09 million tonnes in the first 11 months of the year, or 353,115 bpd, up 165.3% from 6.07 million tonnes over the same period a year earlier.

(GRAPHIC: South Korea's monthly crude oil imports - https://fingfx.thomsonreuters.com/gfx/editorcharts/SOUTHKOREA-CRUDE/0H001QXQ29Y3/eikon.png)

Historically one of Asia's major Iranian oil buyers, South Korea again did not import oil from Iran in November. Iranian crude imports have remained zero since May with the end of waivers on U.S. sanctions on shipments.

For the January-November period of 2019, the country's total Iranian crude oil imports dropped 45.9% to 3.87 million tonnes, or 93,356 bpd, compared with 7.15 million tonnes over the same period a year earlier.

Overall, South Korea's November crude oil imports fell 2.1% year-on-year to 12.44 million tonnes, or 3.04 million bpd, according to the data.

Crude oil shipments from Saudi Arabia, South Korea's top crude oil supplier, were 3.22 million tonnes in November, or 787,837 bpd, down 15.9% from 3.84 million tonnes amid ongoing OPEC-led supply cuts.

In the first 11 months of the year, South Korea's crude oil imports were 131.11 million tonnes, or 2.88 million bpd, down 3.8% from 136.22 million tonnes.

The country's final crude oil import data will be released later this month.

By Jane Chung