Venezuela's chief prosecutor said Tuesday that he had placed former state oil company boss Rafael Ramirez under investigation for corruption. 

"We have decided to open a criminal investigation into citizen Rafael Ramirez," prosecutor Tarek William Saab said on state television.

Ramirez led PDVSA for a decade before becoming Venezuela's ambassador to the UN, a post from which he resigned last week -- saying it was at the request of President Nicolas Maduro.