LEVOCA, CZECHOSLOVAKIA, JULY 5 -- Tens of thousands of Roman Catholics, led by hymn-singing youths, journeyed to the 700-year-old shrine above this walled town today in a resolute show of growing religious commitment despite some of Eastern Europe's most determined efforts at suppression.

Ignoring plainclothes police who snapped their photos and occasionally searched their knapsacks, groups of young people and families from around Slovakia, Czechoslovakia's eastern republic, spent the night praying and singing at the Basilica Minor of Mary in Visitation, the Slovak nation's most important shrine.

This morning, thousands more trudged up the steep, two-mile-long paths to the yellow church and cheered the region's leading cleric as he invoked the guidance of Polish-born Pope John Paul II and spoke of Slovakia's stubborn devotion to its church, which faces communist government controls among the most severe in the Soviet Bloc.

"We want to show that the respect of the Slovak nation for the mother of God is still alive, and that it is a manifestation of the Christian faith in Slovakia," Stefan Garaj, the vicar capitular of the diocese of Spis, told the crowd of more than 20,000 that spread across the green pasture sloping down from the basilica. "All believers in Slovakia are united here in this moment."

The priest's words, although mild by the standards of the strong Catholic establishment in nearby Poland, reflected the growing confidence of the church in Slovakia, where up to 80 percent of the 5 million population are now reported by church activists to be Catholics.

Slovakia's revival of Catholic faith has been perhaps the strongest example of what has become a region-wide phenomenon in Eastern Europe, marked by huge participation in pilgrimages and other religious festivals. Since 1983, more than 100,000 people have been reported each year at Levoca's pilgrimage, and priests here said 120,000 were expected to visit the shrine this weekend.

Today, as in other recent years, the young were the vanguard of this mass movement. Beginning yesterday afternoon, bands of students and workers in their teens and early 20s marched with knapsacks, crosses and guitars in a seemingly perpetual stream up Marian Hill, singing songs they learned in fellowship groups often organized in defiance of authorities.

"Remember, if anyone asks you where you're from, say Levoca, not Bratislava," one youth coordinator told a singing group of about 30 youths who had traveled from the Slovak capital, about 250 miles away, in nominal violation of official restrictions on the activity of church groups. Turning to a visitor, he added cheerfully: "We are working in the system and we are good citizens. But we cannot accept the official ideology when it tries to make us atheists."

Following the custom of recent years, authorities kept uniformed police away from Levoca's pilgrimage site but took steps to divert or intimidate travelers. Youths in the area around this town of 11,000 were pressed to participate in an officially sponsored folklore festival scheduled for this weekend in the nearby town of Vychodnia. Police manning checkpoints on the roads into Levoca stopped some cars and buses and recorded the names of travelers, witnesses said.

At the same time, officials appeared to acknowledge the needs of the pilgrims for the first time, by setting up stands along the route to the shrine selling food, juices and alcoholic drinks.

"The police are here in great numbers, but they do not interfere, only look and hear and take photos," said a veteran Catholic organizer. "Later they will call in some of those they identify for interrogations."

Although government officials deny that simple believers are still subjected to such pressure, Czechoslovakia continues to carry out overt measures to isolate religious activists long after neighboring Poland and Hungary have adopted a more tolerant line.

Priests and bishops must obtain state licenses that strictly limit where they can work and many clergy are pressed to join a state-sponsored movement condemned by the Vatican.

The Spis diocese around Levoca, like most of the country's 13 dioceses, has no bishop because of resistance by authorities to new clerical nominations. Many would-be priests and even bishops in Slovakia have been forced to work clandestinely.

Licensed priests risk a two-year prison sentence if they work outside their parishes. Teen-agers who participate in church groups sometimes are threatened with the denial of entrance to a university, activists said.

Some of those who attended this weekend's pilgrimage said the revival of interest in religion, especially among youth, had been spurred in part by the official repression.

"When something is repressed for so long, people begin to ask why," said a shaggy blond student from southern Slovakia, who, like all of those interviewed, refused to give his name because he feared official reprisals. "Those people look into the church, and many of them discover that it offers an alternative to the life they have known."

Other activists traced the renewal to the long history of close bonds between society and the Catholic Church in Slovakia, in contrast to the often troubled church history in the neighboring Czech lands of Bohemia and Moravia.

"Thanks to the church our small nation has been able to preserve its language and its cultural identity for more than 1,000 years," said a medical student. "It is in the church that the Slovak nation finds its history."

For the young people who gathered in cozy circles on the meadows and woodlands around the shrine this weekend, the biggest reward seemed to be fellowship. "The most important thing for young people is that they can meet people here who have the same feelings, sing the same songs, have the same beliefs," said a 20-year-old pilgrim.

Although thousands of older people, ranging from couples with children to wrinkled peasants in scarves and flowered skirts, also attended the masses, many of the sermons were directed at the new generation.

One priest quoted lyrics by the Beatles to press a point about how to behave in marriage. Another raised the problem of AIDS, saying that the best prevention was "what Moses said {against adultery} when he came down from the mountain."

"We must prove ourselves in history," said the officiating vicar, Garaj, in his sermon. "Only those peoples prove themselves who know who they are, where they came from and where they are going. You have come here and you go to other pilgrimages to prove that you have faith in Mary."