(Reuters) - The International Atomic Energy Agency (IAEA) said on Thursday it was probing a Ukrainian report that a missile had flown directly over a nuclear power station, saying this would be "extremely serious" if true.

       IAEA Director General Rafael Grossi said Kyiv had formally told it on Thursday the missile flew over the south Ukraine plant on April 16. The facility is near the city of Yuzhnoukrainsk, some 350 km (220 miles) south of Kyiv.

       "Had such a missile gone astray, it could have had a severe impact on the physical integrity of the plant, potentially leading to a nuclear accident," he said in a statement.

       Grossi did not say who had fired the missile but Kyiv had earlier accused Moscow of sending rockets directly over nuclear plants.

       (Reporting by David Ljunggren; Editing by Chris Reese)