* Iran crude imports in March at 570,338 T, up 107.5 pct
* Jan-March Iran oil imports at 114,115 bpd, down 16 pct
* Jan-March Iran oil imports below 2014 import avg
* Total crude imports in March at 11 mln T, up 8.7 pct y/y
By Meeyoung Cho
SEOUL, April 15 (Reuters) - South Korea's imports of Iranian crude doubled in March from a year earlier but the country's oil shipments from the OPEC country in the first quarter of this year fell 16 percent year- on-year to meet international sanction requirements.
Seoul imported 570,338 tonnes of crude oil from Tehran last month, or 134,857 barrels per day (bpd), compared with 274,808 tonnes a year ago, preliminary customs data from the world's fifth-largest crude oil importer showed on Wednesday.
Asia's fourth-largest economy brought 1.4 million tonnes or 114,115 bpd of crude from the Middle Eastern country in the first three months of this year, below 136,281 bpd in the same period of last year and last year's average of 125,000 bpd.
Iranian crude shipments in 2014 were 6.2 million tonnes, or 124,497 bpd, down 7.1 percent from the 2013 average of 134,000 bpd, according to the data and Reuters calculations in January.
Iran and the United States, Britain, France, Russia, China, and Germany reached a preliminary deal on Iran's disputed nuclear programme earlier this month and are aiming to reach a final accord by the end of June.
Under current sanctions, big Asian buyers, including South Korea, should hold their crude imports from Tehran at end-2013 levels. Of South Korea's four refiners, only SK Energy Co Ltd and Hyundai Oilbank Co Ltd import Iranian oil, and their imports fluctuate each month.
From Mexico, meanwhile, South Korea imported 135,707 tonnes, or 32,088 bpd, in March, paying about $52 per barrel, according to Reuters calculation based upon the customs data. GS Caltex Corp has bought the oil for the first time in 25 years to take advantage of low prices.
Overall, South Korea imported 11.05 million tonnes of crude last month, or 2.61 million bpd. That was 8.7 percent higher than the 10.16 million tonnes imported in March of 2014, the customs data showed.
Final data for last month's crude oil imports, which will include greater detail, will be available from state-run Korea National Oil Corp later this month.