KYIV, July 9 (Reuters) - Ukraine said on Wednesday it had detained a Chinese father and son, both suspected of spying on its prized Neptune anti-ship missile programme, a key part of Kyiv's growing domestic arms industry critical to its defence against Russian invaders. The announcement by the Security Service of Ukraine (SBU) follows assertions by Kyiv in recent months that Beijing, which has sought to project an image of neutrality, is helping the Kremlin's war effort.