MOSCOW, April 15 (Reuters) - Russia's seaborne oil product exports fell 4.2% in March from the previous month to 10.178 million metric tons due to unplanned maintenance at refineries and a uel export ban, data from industry sources and Reuters calculations showed.

Russia's daily offline primary oil refining capacity has jumped by around a third in March to 4.079 million metric tons from February due to drone attacks, Reuters calculations based on data from industry sources showed.

Last month, a fire broke out after a Ukrainian drone attack at the Norsi refinery, Russia's fourth largest refinery owned by Lukoil, and at three oil refineries, controlled by Rosneft: Ryazan, Syzran and Kuibyshev.

Russia also imposed a six-month ban on gasoline exports from March 1 to keep domestic prices stable.

Total oil product exports via the Baltic ports of Primorsk, Vysotsk, St. Petersburg and Ust-Luga last month decreased 9.7% from February to 5.680 million tons, data from market sources showed.

Fuel exports via Russia's Black Sea and Azov Sea ports rose in March by 7.2% from the previous month to 3.741 million tons.

Oil products export supplies from Russia's Arctic ports of Murmansk and Arkhangelsk fell last month by 64.4% from February to 43,400 tons.

Fuel export loadings at Russia's Far East ports decreased by 1.6% in March month-on-month to 713,000 tons, data from sources and Reuters calculations showed.

(Reporting by Reuters Editing by Louise Heavens)