SULAIMANIYA/MOSUL, Iraq (Reuters) - Three rockets launched near Erbil International Airport in the semi-autonomous Kurdistan Region of Iraq were intercepted mid-air and a fourth landed near the headquarters of an Iranian opposition group, Kurdish Peshmerga sources said on Wednesday. Sirens were heard inside a military base housing U.S. troops, local Kurdish media said. It was not immediately clear if U.S. troops, the Iranian opposition group, or both were the target of the attack. Kurdish security sources said the rockets were launched from the northern Iraqi province of Nineveh.