TOKYO, Dec 1 (Reuters) - Japan is "concerned" that the U.S. military continues to fly the Osprey aircraft despite the government's request to ground them until their safety is confirmed, Japan's top government spokesperson said on Friday.

Speaking at a regular news conference, Chief Cabinet Secretary Hirokazu Matsuno said the government had officially made the grounding request, when asked about the Pentagon's statement a day earlier that it was not aware of such a request.

Japan said on Thursday it had asked the U.S. to suspend all non-emergency V-22 Osprey flights over its territory after one fell into the sea on Wednesday in western Japan. (Reporting by Mariko Katsumura and Chang-Ran Kim)