SEOUL, Sept 28 (Reuters) - North Korea fired an unidentified projectile towards the sea off its east coast on Tuesday, South Korea"s military said, amid Pyongyang"s calls for the United States and South Korea to scrap their "hostile policy". The South Korean military did not give any more details, while Japan"s defence ministry said it appeared to be a ballistic missile, without elaborating. The announcement came just before North Korea"s ambassador to the United Nations urged the United States to give up its hostile policy towards Pyongyang and said no one could deny his country"s right to self defence and to test weapons. North Korea accused Seoul and Washington of "double standards," saying they denounced its weapons development while continuing their own military activities. read more On Sept. 15, North and South Korea both test fired ballistic missiles, the latest volley in a race in which the rivals have been developing increasingly sophisticated weapons. read more At the time, Washington condemned the North Korean test - and a separate test days earlier of what experts said could be its first cruise missile capable of carrying a nuclear warhead - as a threat to its neighbours. It did not mention Seoul"s test of a submarine-launched ballistic missile (SLBM). North Korea has since released a series of statements saying it is willing to restart stalled inter-Korean talks and consider another summit if the South scraps its double standards and hostile policy toward the North. read more The U.S. military"s Pacific Command and the U.S. State Department did not immediately respond to requests for comment. At the U.N. General Assembly, North Korea"s U.N. envoy, Kim Song, said the country was just shoring up its self-defence and if the United States dropped its hostile policy, it would respond "willingly at any time" to offers to talks. read more "But it is our judgment that there is no prospect at the present stage for the U.S. to really withdraw its hostile policy," Kim said.