"The general conditions and cardio-respiratory conditions of the Holy Father have further worsened. A gradual worsening arterial hypotension has been noted, and breathing has become shallow," the Vatican press office said.

"The clinical picture indicates cardio-circulatory and renal insufficiency. The biological parameters are notably compromised. The Holy Father, with visible participation, is joining the continual prayers of those assisting him."

Vatican spokesman Joaquin Navarro-Valls said earlier that the pope was in "very serious condition" Friday afternoon, but he is "lucid, fully conscious" and "very serene."

Navarro-Valls also said earlier that the pope's blood pressure was "unstable" and that he "... asked for the Holy Scriptures to be read to him."

--CNN