LYON, France (AP) _ Some 50,000 youths gave Pope John Paul II a rousing welcome Sunday at a rally featuring dancing and a hymn set to disco music, and the pontiff urged the young people to fight religious indifference, terrorism and hunger.

The youths at Gerland soccer stadium cheered wildly, stomped and waved blue and white scarves as the pontiff blew kisses from an open popemobile. The evening rally was on the second day of a four-day visit to France, and it gave John Paul his warmest reception so far.

A dance troupe performed a modern version of the song ''Rise Up and Walk,'' set to a pulsing disco beat, and acted out religious themes.

As John Paul addressed the rally, aides said the Vatican was working on personal messages from the pope to leaders all over the world, urging them to observe a one-day truce in all conflicts on Oct. 27.

The pontiff announced the idea Saturday, saying it would coincide with an international day of interfaith prayer for peace that he is organizing in Assisi, Italy the same day.

The pope's appeal for youths to join together to combat modern problems was well received.

''He's created a dialogue between him and young people,'' said Emilia Sardo, a 24-year-old Roman Catholic who traveled here from Paris for the event.

But like other young people interviewed, she said she is not a regular church-goer and does not agree with all of the pope's stands, particularly on issues like sexual behavior and birth control.

Earlier, John Paul's attacks on abortion and divorce during a rural Mass in the Burgundy town of Paray-Le-Monial evoked a tepid response from the audience.

Though 80 percent of the French people consider themselves Catholic, polls indicate a steady erosion in the number who attend Mass regularly and who support the pope's positions on moral issues, particularly sexual matters.

Speaking in an open field before an estimated 100,000 people waving colored scarves, the pope urged Catholics to work at conserving ''a heart of flesh, a heart that has a human sensibility and a heart that lets itself be conquered by the Holy Spirit.''

He said the increasing number of broken families and abortions were ''signs of a real and true sickness that hits at people, couples, children and society itself.''

The leader of the world's 800 million Catholics was surrounded by heavy security as he traversed the countryside before returning to Lyon for the youth rally.

Police carefully scrutinized the crowds at the Mass and during a visit to a small ecumenical community called Taize. There, pathways were thick with gendarmes, and sharpshooters watched from a belltower.

John Paul met at the tiny village with Brother Roger, the 71-year-old Swiss Protestant who in 1940 founded the Taize Community, devoted to praying for the reconciliation of all Christian churches.

The 80 brothers at Taize, from 20 countries, adhere to no organized church. Their community has become a major pilgrimage site, particularly for the young.

''By listening to the criticisms and suggestions of Christians of different churches ... you will not disappoint the young people,'' the pope told the brothers, noting that ecumenism for him was ''a pastoral priority.''

The youth rally ran an hour over schedule and John Paul arrived late at the Notre Dame de Fourviere basilica, on a hill overlooking Lyon and its Rhone and Saone Rivers, for a ceremony to bless the city.

Speaking from a balcony of the 19th-century church encased in bulletproof glass, he apologized to the crowd for being tardy and wished them ''prosperity and peace.''

The pontiff also met with nuns, brothers and members of secular institutions at Fourviere.