UNITED NATIONS - Turkey on Wednesday asked the UN Security Council to take the "necessary action" to stop Syrian aggression and ensure that Syria respect its territorial sovereignty after a mortar bomb fired from Syria killed five Turkish civilians."This is an act of aggression by Syria against Turkey," Turkish UN Ambassador Ertugrul Apakan said in a letter to the president of the 15-nation Security Council, Guatemalan Ambassador Gert Rosenthal."It constitutes a flagrant violation of international law as well as a breach of international peace and security," said the letter, which was obtained by Reuters.