(Reuters) – Minnows Uruguay stunned rugby sevens powerhouses Fiji and New Zealand in two astonishing back-to-back upsets on a remarkable opening day of the world sevens series’ Perth leg on Friday. The South Americans launched an epic comeback to beat Olympic silver medalists Fiji 24-17 and followed that with an astonishing 17-12 win over the All Blacks. Fiji, who had beaten Uruguay 70-7 in Cape