* Aug Iranian crude imports up 40.2 pct y/y at 1.55 mln T
* Jan-Aug oil imports from Iran jump 46.7 pct to 12.22 mln T y/y
* Total crude imports in Aug at 13.55 mln T, up 17.7 pct y/y
* Imports 98.23 mln T crude oil in Jan-Aug, up 3.9 pct y/y (Adds detail on oil imports, background)
SEOUL, Sept 15 (Reuters) - South Korea's imports of Iranian crude oil increased 40.2 percent in August from the same month a year earlier, with its refiners snapping up competitively priced cargoes from the Middle Eastern nation.
South Korea, the world's fifth-biggest crude importer, brought in 1.55 million tonnes of Iranian crude last month, or 365,641 barrels per day (bpd), compared with 1.1 million tonnes in the same month in 2016, customs data showed on Friday.
Iran has been boosting oil production since Western sanctions over its nuclear programme were lifted last year, aiming to increase crude output to 4.5 million bpd within five years.
In the first eight months of 2017, South Korea's oil imports from Iran were 12.22 million tonnes, or 368,529 bpd, up 46.7 percent from 8.33 million tonnes during the same period the year before, the data showed.
South Korea, one of Iran's major Asian clients, mainly purchases an ultra-light oil, also known as condensate, from the country, but a breakdown of imports is not available. It uses condensate to produce more expensive fuels like naphtha,
For Asian buyers, Iran set the official selling prices of its light and heavy grades at 18 cents and $1.17 respectively below the Oman/Dubai average for August, while it raised September Iranian Light oil prices 20 cents higher than those in August.
While the Organization of Petroleum Exporting Countries (OPEC) members and some non-members strive to curb their production to clear a global oil glut, Iran is not capping its output as it was excluded from the OPEC-led supply cut deal to reduce their production by around 1.8 million bpd until next March.
Meanwhile, South Korea imported 4.05 million tonnes of crude, or 957,283 bpd from Saudi Arabia, up 9.8 percent from 3.69 million tonnes a year ago, the data showed.
Overall, South Korea's total crude imports in August rose 17.7 percent to 13.55 million tonnes, or 3.20 million bpd, according to the data.
In January-August of 2017, South Korea shipped in 98.23 million tonnes of crude, or 2.96 million bpd, up 3.9 percent from 94.55 million tonnes over the same period last year.
State-run Korea National Oil Corp (KNOC) is set to release South Korea's final data for August crude imports later this month. (Reporting by Jane Chung; Editing by Joseph Radford)