* Crude imports from Iran in March at 4.02 mln bbls -data
* Total March crude imports at 73.2 mln bbls, down 0.4 pct y/y
* Dec 2012-March 2013 Iran crude imports at 162,107 bpd (Adds details)
By Meeyoung Cho
SEOUL, April 22 (Reuters) - South Korea's imports of Iranian crude in March fell 16.2 percent from a year ago to 4.02 million barrels, data from the state-run Korea National Oil Corp showed on Monday, after its biggest refiner SK Energy shut a crude unit for maintenance.
The world's No.5 crude oil buyer and one of Iran's top four customers bought 129,710 barrels per day (bpd) in March, down 8.6 percent from a month ago although more than double the volume projected earlier based on loading data.
But imports from sanctions-hit Iran should surge month-on-month to 190,000 bpd in April as SK Energy's 110,000-bpd crude distillation unit returned to operation on April 16 after 30 days of maintenance.
U.S. and European Union sanctions aimed at choking the flow of oil money into Iran and forcing Tehran to negotiate curbing its disputed nuclear programme have cut Iran's crude exports to Asian importers such as Korea.
Crude imports from Iran in the first three months of the year dropped 21.6 percent from the same period last year to 13.89 million barrels, the data showed.
South Korea's total crude oil imports came in at 73.22 million barrels in March, down 0.4 percent from a year earlier, according to KNOC's data.
Its two buyers of Iranian crude, refiners SK Energy and Hyundai Oilbank, are shutting a combined 560,000 bpd of refinery capacity for planned maintenance between March and June.
South Korea, which reduced crude imports from Iran by more than a third to 153,400 barrels per day last year, is aiming for a 20 percent cut in the six months to May 31 from a year ago to secure an extension to a waiver from U.S. sanctions when Washington examines the issue in May.
Korea imported 162,107 bpd of Iranian oil from December through March, according to Reuters calculations based on the latest KNOC data, versus 184,727 bpd from December 2011 through May 2012.
To meet the target of reducing Iranian imports, South Korea will have to cut 14,326 bpd or 8.8 percent from the December-March rate. (Editing by Himani Sarkar)