VATICAN CITY (Reuters) -Former pope Benedict, a hero to conservative Catholics and who in 2013 became the first pontiff in 600 years to step down, is "very sick", his successor Pope Francis said on Wednesday, asking Church members to pray for him.
Bishops from Europe, the United States and beyond, urged the faithful to keep Benedict in their thoughts, after the Vatican followed Francis' announcement with a statement saying Benedict had suffered a sudden "worsening" of his health.
"I would like to ask all of you for a special prayer for Pope Emeritus Benedict, who, in silence, is sustaining the Church," Francis said in Wednesday's surprise announcement made at the end of his weekly general audience.
"Let us remember him. He is very sick, asking the Lord to console and sustain him in this witness of love for the Church, until the end," Francis said, speaking in Italian.
The Vatican statement said Benedict was receiving constant medical attention and his condition was under control.
Francis, who visited the former pontiff after making the announcement, has often praised Benedict, saying it was like having a grandfather at home. But the presence of two men dressed in white in the Vatican has at times been troublesome.
Conservatives have looked to the former pope as their standard bearer and some ultra-traditionalists even refused to acknowledge Francis as a legitimate pontiff.
They have criticised Francis for his more welcoming approach to gays and to Catholics who divorced and remarried outside the Church, saying both were undermining traditional values.
Catholic Church leaders from Germany, Britain, the United States and elsewhere urged the faithful on social media to join prayers for Benedict, who was pope for almost eight years before he retired.
"This morning I received the news that there is great concern in Rome about the health of the Pope Emeritus. And so we especially want to include him in our prayers," German Cardinal Reinhard Marx, Archbishop of Munich, told churchgoers.
Cardinal Matteo Zuppi, head of the Italy's bishops conference, asked Italians to keep Benedict in their thoughts "in this moment of suffering and trial".
Until a few weeks ago, those who had seen Benedict said his body was very frail but his mind was still sharp.
Italian news reports said he had been suffering from respiratory problems over the Christmas period.
The Vatican did not give any details of his condition. There was no immediate response to a request for comment from Benedict's private secretary.
One of the latest known photographs of Benedict was taken on Dec. 1, when he met the winners of a prize for theologians named after him. He was seated and looked exceptionally weak.
Since resigning Benedict has been living in a former convent inside the Vatican gardens, with his secretary, Archbishop Georg Ganswein, and a few other aides and medical staff.
Benedict announced his intention to resign on Feb. 11, 2013, shocking a meeting of cardinals. He said he no longer had the physical and mental strength to run the Church.
He formally stepped down on Feb. 28 that year, moving temporarily to the papal summer residence south of Rome while cardinals from around the world came to Rome to choose his successor.
Francis, the first pope from Latin America, was elected to succeed him on March 13, 2013.
Benedict, the first German pope in 1,000 years, had been elected on April 19, 2005 to succeed the widely popular Pope John Paul II, who reigned for 27 years.
Cardinals had chosen Benedict from among their number seeking continuity and what one called "a safe pair of hands".
For nearly 25 years, as Cardinal Joseph Ratzinger, he was the powerful head of the Vatican's doctrinal office, then known as the Congregation for the Doctrine of the Faith (CDF).
(Reporting by Philip Pullella; Editing by Andrew Heavens and Edmund Blair)