UPDATE 1-S.Korea's Dec Iranian crude oil imports drop over 30 pct y/y

* S.Korea's Dec Iranian crude imports at 1.08 mln T

Imports from Iran up 29.1 pct at 18.07 mln T in 2017

* Dec total crude imports at 13.25 mln T vs 13.24 mln T y/y

* S.Korea's 2017 crude imports up 3.3 pct at 148.68 mln T on-year (Adds detail, background)

By Jane Chung

SEOUL, Jan 15 (Reuters) - South Korea's imports of Iranian crude oil dropped 30.6 percent in December from the year before, while inbound shipments from the Middle Eastern nation over the whole of 2017 jumped by 29.1 percent, customs data showed on Monday.

The world's fifth-largest crude importer in December brought in 1.08 million tonnes of Iranian crude, or 255,081 barrels per day (bpd), down 30.6 percent from 1.55 million tonnes a year earlier.

Major Asian crude buyers including South Korea have snapped up purchases of Iranian oil since sanctions over the nation's disputed nuclear programme were lifted a couple of years ago.

South Korea mainly buys condensate from Iran, an ultra-light form of crude, but its data does not provide a breakdown on categories of imports.

Despite a push by Iran to boost exports, its condensate shipments have been dented by a technical problem at the South Pars oil field.

Iranian oil and shipping sources said earlier this month that oil output from the third-biggest producer in the Organization of the Petroleum Exporting Countries (OPEC) had stayed around 3.8 million bpd, despite political unrest in the country around that time.

For the whole of 2017, South Korea's oil imports from Iran rose 29.1 percent to 18.07 million tonnes, or 362,884 bpd, versus 14 million tonnes in 2016, according to the customs data.

In total, South Korea imported 13.25 million tonnes of crude oil in December, or 3.13 million bpd, up 0.1 percent from 13.24 million tonnes a year ago, the data showed.

South Korea's crude oil imports from Saudi Arabia last month edged down 0.2 percent from a year ago to 4 million tonnes, or 946,615 bpd, with total 2017 crude intake from its top oil supplier falling 1.7 percent to 43.06 million tonnes from 2016.

In full-year 2017, South Korea's crude oil imports increased 3.3 percent to 148.68 million tonnes, or 2.99 million bpd, versus 130.71 million tonnes the previous year.

Final data for South Korea's December crude imports data will be released by state-run Korea National Oil Corp (KNOC) later this month.

(Reporting by Jane Chung; Editing by Joseph Radford)