MOSCOW, Aug 11 (Reuters) - Moscow and Kyiv accused each other of starting a fire on the grounds of Europe's largest and now Russian-occupied Zaporizhzhia nuclear power plant in Ukraine on Sunday, with both sides reporting no sign of elevated radiation.

The U.N.'s International Atomic Energy Agency (IAEA) nuclear watchdog, which has a presence at the vast six-reactor facility, said its experts had seen strong, dark smoke coming from the northern area of the plant in southern Ukraine following multiple explosions.

Russian state news agencies, TASS and RIA, cited the country's nuclear energy company Rosatom as saying the main fire was extinguished shortly before midnight on Sunday.

The fire comes less than a week after Ukraine's forces launched their largest incursion into Russian territory since the war-start in 2022, a surprise move that has brought conflict into a new phase, after weeks of Moscow's battlefield gains.

Ukraine's nuclear power company Energoatom said in a statement on the Telegram messaging app that one of the cooling towers and other equipment were damaged.

Russia's TASS agency also reported, citing Rosatom's statement, that a cooling tower was damaged. Citing local Russian emergency ministry representatives, TASS said it was a non-functioning tower.

Russia captured the plant from Ukraine shortly after launching its full-scale invasion on its smaller neighbour in 2022, an attack described by Moscow as a "special operation". The plant's six nuclear reactors are in cold shutdown.