Pope John Paul II, whose indomitable will and uncompromising belief in human dignity helped bring down communism in Eastern Europe and reshaped Christianity's relationship to Judaism, died today. He was 84.

The Polish-born John Paul, indisputably the most influential pope of the 20th century, died in his apartment overlooking St. Peter's Square after suffering heart failure and septic shock during treatment for an infection, the Vatican said.

The announcement came from papal spokesman Joaquin Navarro-Valls and was distributed to journalists via e-mail.

"The Holy Father died this evening at 9:37 p.m. (11:37 a.m. PST) in his private apartment. All the procedures outlined in the apostolic Constitution 'Universi Dominici Gregis' that was written by John Paul II on Feb. 22, 1996, have been put in motion."

A Mass was scheduled for St. Peter's Square for Sunday morning.

The pope died after suffering heart and kidney failure following two hospitalizations in as many months. Just hours earlier, the Vatican said he was in "very serious" condition but had responded to members of the papal household.

The pope underwent two hospitalizations within the last month. Breathing problems forced him to undergo surgery Feb. 24 to insert a tube in his throat to aid breathing.

His health declined dramatically over the last week, worsening after he developed a high fever from a urinary tract infection. On Friday, the Vatican said the pope's breathing had turned shallow and his kidneys further deteriorated. He had received the sacrament commonly known as the last rites Thursday evening.

Through it all, the pope chose to project his gradual incapacitation as a final Christian message of redemption through suffering. For the first time since his papacy began in 1978, he was absent from Easter rituals, which began on Palm Sunday. On Easter Sunday, he appeared before thousands of pilgrims and struggled to speak, but ultimately failed.

The first non-Italian elected pope in 456 years, John Paul energized the papacy through much of his reign, traveling as evangelist and champion of religious freedom even as he imposed a rigorous moral discipline and more centralized authority on his sometimes rebellious 1-billion-member church.

In his 26-year papacy, John Paul made 104 trips outside Italy to 129 nations, going as a pastor to countries such as Brazil, where Catholics are the majority, and Japan, where they are a minority.

He preached along the equator and inside the Arctic Circle. He preached on sere Andean mountaintops and on lush tropical islands, in famous European cathedrals and in bullet-pocked African country churches. And he preached amid the wreckage of fratricidal wars in Sarajevo and Beirut.

On his travels to Poland, it was his unflinching support for the Solidarity trade union movement that helped embolden first his homeland and then half the European continent to topple communist regimes.

A witness to the Holocaust as a young man, John Paul led the Roman Catholic Church on a pilgrimage of repentance and reconciliation with Jews, culminating in the establishment of diplomatic relations with the state of Israel.

In his final years, he made a crowning pilgrimage to the Holy Land and became the first Roman Catholic leader in nearly 1,300 years to visit Greece, trying to bridge the centuries-old theological divide with Eastern Orthodoxy.

By 2003, John Paul's journeys had been scaled back, but he continued to press on. His final trip was in August 2004, returning to France to visit the miracle shrine of Lourdes. It was a poignant backdrop for the frail and ailing pontiff. Surrounded by other sufferers, many seeking miracle cures, he struggled to read his sermon and was heard to whisper to an aide in Polish, "Help me." After a drink of water, he said softly, "I must finish." And finish the speech he did.

John Paul, ever mindful of his own mortality, increasingly spoke retrospectively about his life as a priest. "After almost 60 years of priesthood," he told 12,000 cheering youths last summer in Switzerland, "it is beautiful to be able to spend yourself until the end for the cause of the reign of God."

In that cause, John Paul confronted dictators of the political left and right, coaxed U.S. presidents on foreign policy issues such as Cuba and Iraq, reached out to the elderly and reined in theologians, priests and nuns who strayed from his view of Catholic orthodoxy. He wrote more encyclicals and put more individuals on the road to sainthood than any pope in history.

He apologized to Jews, women, Orthodox Christians and others for his church's failings and sins against them throughout history. He apologized to Muslims for the Crusades, which ravaged the Holy Land from the 11th through the 13th centuries.