SEOUL - South Korea's crude oil imports from the United States more than doubled in September, while its imports of Iranian oil remained zero for a fifth month in a row due to U.S. sanctions, customs data showed on Tuesday.

U.S. crude oil imports were 1.62 million tonnes in September, or 395,190 barrels per day (bpd), compared with 668,704 tonnes a year earlier, according to the customs data.

In September, the United States ranked as South Korea's No.3 crude oil supplier after Saudi Arabia and Kuwait.

South Korea, a big buyer of Iranian oil, halted importing oil from Tehran in May after the U.S. government announced an end to waivers on U.S. sanctions against Iran that allowed South Korean oil buyers to buy Iranian oil, mainly condensate, or an ultra-light form of crude oil.

In September last year, South Korea did not import oil from Iran ahead of U.S. sanctions.

For the January-September period, South Korea's oil intakes from Iran were 3.87 million tonnes, or 103,957 bpd, versus 7.15 million tonnes during the same period a year earlier, according to the data.

In total, South Korea imported 10.48 million tonnes of crude oil in September, or 2.56 million bpd, down 3.3% from 10.83 million tonnes a year earlier.

Imports from Saudi Arabia, South Korea's top oil supplier, decreased 16.7% to 2.84 million tonnes in September, or 694,217 bpd, from a year earlier.

The drop in Saudi crude imports follows attacks on Saudi Arabia's key oil facility in mid-September, knocking out more than half of the kingdom's crude oil production.

In September, South Korea also imported 81,011 tonnes of crude oil from Canada and 77,580 tonnes of crude oil from Papua New Guinea, the data showed.

In the first nine months of the year, the country's crude imports fell 2.6% to 107.63 million tonnes year-on-year, or 2.89 million bpd, according to the data.

State-run Korea National Oil Corp (KNOC) will release the country's final crude oil imports data later this month.

(Editing by Deepa Babington) ((jane.chung@thomsonreuters.com; +82 2 6936 1459;))