ROME, August 9 (AP)--Thousands of arch-conservative Roman Catholics conducted their own defiant Holy Year pilgrimage Wednesday, celebrating Mass in Latin and urging the church to return to that and other traditions it largely abandoned 35 years ago.

The surprise Mass unfolded under the trees of a dusty Rome hilltop--across the Tiber River from far-off St. Peter's, where followers of the late ultra-traditionalist Archbishop Marcel Lefebvre said the Latin liturgy really belongs.

Adherence to the old Latin-language Mass contributed to Pope John Paul II's excommunication of Lefebrve in 1988, and to the church's first major schism in 130 years.

"It is like a crucifixion--the crucifixion of tradition," Bishop Bernard Fellay told thousands of worshippers.

"We ask the Holy Father to give us back the Mass," the white-and-gold-robed prelate appealed, urging Pope John Paul II to return to old ways so that God "may reign again in this church, in this town, in this whole Earth."

The alternative, he said, is "like suicide--because the church is tradition."

The pilgrimage by the 5,000 to 8,000 ultra-traditionalists was for Rome a surprise event not listed on the Holy Year calendar.

A Holy Year, like this one, is a year proclaimed by the pope as one especially favorable for pilgrimages and other observances. Holy Years have come to be celebrated every 25 years.

Holy Year officials cooperated with the pilgrimage to the extent of easing basilica tours for the large group and providing the city's blue-and-yellow garbed volunteer guides for the Mass--but not to the extent of opening the city's basilicas for the now-eschewed Latin Mass.

Look "where we have to celebrate Mass, in this place," Fellay said under a velvet pavilion on the hill. "The Mass, the Roman Mass, has no right [today] to be celebrated in Rome!"

Lefebvre and now his followers reject liberal reforms of the 1962-65 Vatican Council--Vatican II--that were meant to make the church more accessible to the laity. The innovations included giving up the Latin Mass in favor of those in the local language of each land and turning priests around to face the congregation rather than the altar.

The French-born Lefebvre died in 1991; adherents of his conservative beliefs say they number in the hundreds of thousands today.

Followers from Europe, the Philippines, North America, and elsewhere came to Rome for a three-day pilgrimage ending Thursday.

Young and old lined up to kneel in confession before priests on folding chairs under the shade. Black-robed nuns hovered on the fringes of the crowd, chatting.

"We're here to show our loyalty to Rome, to the Holy Father," said the Rev. Edward MacDonald of Dublin, Ireland. "We're not in schism at all."

"We just hope and pray that they return to the traditional faith," added Dan Rathke, a lay follower from St. Paul, Minn.

The Vatican has said nothing publicly about the Rome appearance of the renegade movement's pilgrims, who made the traditional Holy Year trip through the Holy Door at St. Peter's on Tuesday.

The church has made overtures to bring priests and others in the movement back into the fold.

The church also occasionally grants special permission to priests wishing to use the old, Latin Mass.

Fellay told followers their pilgrimage would give heart to many more who secretly want to return to the old ways.

The last church schism, in 1870, was over the issue of papal infallibility.