Claims of a bizarre plot to assassinate Pope Benedict XVI are reverberating through Italy in what observers say signals the latest twist in an increasingly cutthroat internal Vatican power dispute.

The Italian daily Il Fatto Quotidiano published the sensational "mordkomplott" letter detailing an alleged plot against the pope on its front page on Friday. Despite a Vatican spokesman's claiming it was "nonsense not to be taken seriously", the content of the anonymous warning letter, dated 30 December 2011, was reported widely in Italian and German media.

The letter was delivered in early January to the Vatican secretary of state, Tarcisio Bertone, and the pope's private secretary, Georg Gänswein, by Cardinal Darío Castrillón Hoyos of Colombia, according to Il Fatto Quotidiano. The paper suggested it had been written in German to avoid attracting the attention of certain Vatican officials while communicating clearly and directly with close advisers to the pope, who is German.

Labelled "strictly confidential for the Holy Father", the detailed letter reports several conversations that Cardinal Paolo Romeo, the archbishop of Palermo, allegedly had with Italian businessmen in Beijing on a trip last November during which he predicted the pope would die within 12 months and suggested his replacement would be Angelo Scola, the archbishop of Milan.

"This seems something so far from reality and not serious that I don't want to even comment," the Vatican spokesman, Federico Lombardi, said when asked for comment by the paper.

But Castrillón Hoyos felt the threat was serious enough that he suggested the Vatican open an inquiry into exactly what was said during the mysterious China trip, which, if it happened, was not widely reported publicly. Hoyos is older than the 73-year-old Romeo, and part of the more traditionalist wing of the church.

According to Il Fatto Quotidiano, these latest revelations are further proof that a messy internal power dispute is unfolding inside the Vatican. Earlier this month, four clerics publicly defended their management of the sovereign, 108-acre Vatican City, in the heart of Rome, after a former deputy governor levelled harsh criticisms of corruption over how bids and contracts were managed.