http://news.bbc.co.uk/1/hi/world/europe/4402323.stm
Pope John Paul II's health has taken a turn for the worse, the Vatican said.
His breathing is shallow, his blood pressure is low and he is having difficulties with both his heart and his kidneys, a spokesman said.
Millions of Catholics around the world have been praying for the Pope, and a special Mass was being held in Rome as the latest news was announced.
Cardinals - who will elect a new pope - are arriving in Rome from all over the world, the Italian media have reported.
Vatican spokesman Joaquin Navarro-Valls said on Friday evening that the Pope's overall condition had been "notably compromised".
Do not feel shame at showing your emotion and at shedding tears Cardinal Franciszek Macharski
Archbishop of Krakow
Pope 'lucid': Statement What is Anointing the Sick?
But he added that the Pope was visibly participating in prayers around his sickbed.
The Pope's condition deteriorated on Thursday after he developed a urinary tract infection that later brought on "septic shock and a cardio-circulatory collapse".
He was given the Catholic sacrament for the sick and dying - called the Anointing of the Sick.
But the Pope decided not to return to Rome's Gemelli hospital.
He was being treated in his apartment by a team of four top consultants and his private doctor Renato Buzzonetti.
Prayers worldwide
On Friday morning, the Vatican said that though gravely ill, the Pope was stable and conscious.
He was "still lucid, fully conscious and extraordinarily serene", the spokesman said.
St Peter's Square Pilgrims gather in St Peter's Square to pray for the Pope
The Pope was able to make a sign of the Cross on Friday morning as aides read the scriptures to him, he added.
Later, the Vatican announced that the Pope had approved the appointment of 17 new bishops and archbishops and accepted the resignation of six others.
Catholics around the world have been praying for the Pope.
Thousands attended a Mass in Rome's St John in Lateran cathedral on Friday evening presided over by the Pope's vicar, Cardinal Camillo Ruini
Police have imposed traffic restrictions around the Vatican and authorities are making plans to deal with a huge influx of pilgrims anxious to be present in the event of an announcement of the Pope's death.
In the Pope's homeland, Poland, churches have been packed with worshippers.
The Archbishop of Krakow, Franciszek Macharski - a long-time friend of the Pope - told his audience: "Do not feel shame at showing your emotion and at shedding tears."
More than 20,000 Brazilians gathered for a Mass in Sao Paulo, in what the city's archbishop described as an expression of love.
