Zimbabwe police vowed Monday to pursue a crackdown on civic society organisations, saying some Western-backed groups posed a "serious security threat". Police have in recent weeks raided leading human and political rights non-governmental organisations in what activists say is calculated harassment ahead of a constitutional referendum due on March 16. "Some of these NGOs really are going to pose a serious security threat to our country," deputy police commissioner general Innocent Matibhiri told a parliament committee on defence and home affairs.