VIENNA (Reuters) -Below are five facts about the Zaporizhzhia nuclear power plant in Ukraine, the biggest in Europe by capacity, which Russian troops have seized, according to the regional state administration.

       Ukraine said Russian forces attacked the plant in the early hours of Friday, setting an adjacent five-story training facility on fire. The fire was later extinguished.

       * Zaporizhzhia is the largest of Ukraine's four nuclear power plants, which together provide about half the country's electricity.

       * This is the first time war has broken out in a country with such a large and established nuclear power programme, the International Atomic Energy Agency says.

       * Zaporizhzhia's six units each have a net capacity of 950 Megawatts electric, or a total of 5.7 Gigawatts electric, according to an IAEA database. The first unit was connected to the grid in 1984, and the last in 1995.

       * The power plant is operating at just a fraction of its capacity. An internal IAEA notification seen by Reuters on Friday said:

       - Unit 1 is "in outage"

       - Units 2 and 3 "have been disconnected from the grid, and the cool down of the nuclear installation is being carried out"

       - Unit 4 "is in operation at 690 MW power"

       - Units 5 and 6 "are being cooled down".

       * The power plant is of strategic importance to Russia because it is only about 200 km from Crimea, which Russia annexed in 2014.

       (Reporting by Francois Murphy; Editing by Frank Jack Daniel)