AP – Pope Benedict XVI, aboard his popemobile, waves at faithful gathering at the Zagreb Hippodrome prior …

ZAGREB, Croatia – Pope Benedict XVI denounced the "disintegration" of family life in Europe on Sunday and called for couples to make a commitment to marry and have children, not just live together, as he reaffirmed traditional Catholic family values during his second and final day in Croatia.

Benedict also voiced the Vatican's opposition to abortion at an open-air Mass Sunday at Zagreb's hippodrome, the highlight of his trip to mark the local church's national day of families. Tens of thousands of people, waving small plastic Croatian and Vatican flags, began arriving before dawn at the field muddied by overnight thunderstorms.

The sun shone through the clouds as Benedict arrived for the Mass in his white popemobile, waving to the crowd as he looped around the field, which has a capacity of some 300,000 and appeared nearly full with faithful from across Croatia and neighboring countries.

This is Benedict's first visit as pope to Croatia, an overwhelmingly Catholic Balkan nation that is poised to soon join the European Union. The Vatican has strongly supported its bid, eager to see another country with shared values join the 27-member bloc.

Yet while Croatia is nearly 90 percent Catholic, it allows some legal rights for same-sex couples and, thanks to leftover communist-era legislation, permits abortion up to 10 weeks after conception and thereafter with the consent of a special commission of doctors.

In his homily, Benedict lamented the "increasing disintegration of the family, especially in Europe" and urged young couples to resist "that secularized mentality which proposes living together as a preparation, or even a substitute for marriage."

"Do not be afraid to make a commitment to another person!" he said.

He urged parents to affirm the inviolability of life from conception to natural death — Vatican-speak for opposition to abortion, saying "Dear families, rejoice in fatherhood and motherhood!" He also urged them to back legislation that supports families "in the task of giving birth to children and educating them."

His message — delivered mostly in Italian and translated into Croatian — has been received with a resounding welcome in Croatia, which Benedict's predecessor Pope John Paul II visited three times during and after the Balkan wars of the 1990s.

"It's great the pope's here," said Karmela Sokolic, a young girl who said she arrived at the hippodrome at 4 a.m. to snag a place near the altar. "I just love the pope and I love that I am here."

Sister Monica Zvonarek said the pope's presence in Croatia gives hope to all families. "He can encourage us, our politicians to enter in Europe," she said as she waited for the Mass to start.

Monsignor Valter Zupan, in charge of family issues in the Croatian bishops' conference, said Europe had been founded on deeply Christian values about marriage between man and woman, but that these values were being threatened by trends that favor "different types of living together which don't have any foundation in European culture."

Croatia has recognized same-sex couples since 2003 and allows gay partners in relationships of more than three years rights of inheritance and financial support, the same as enjoyed by heterosexual couples who aren't married. There is no gay marriage, however, and gay couples cannot adopt.

"We want our children to continue to call their parents 'mamma' and 'papa' because that's their natural names," he told the applauding crowd. "Children have the right to publicly state that a 'father' and a 'mother' gave them life," he said, adding that the church also had the right to demand the government reverse its abortion law.

As he arrived in Zagreb Saturday on his 19th foreign visit, Benedict urged Croatia to use its new role in the EU to remind Europe about its Christian heritage "as a matter of historical truth" — a constant refrain of this pope who has made fighting Europe's increasing secularization a priority. He also urged young Catholics to hold fast to their faith and values and not be tempted by "enticing promises of easy success."

Later Sunday after Mass, Benedict will pray before the tomb of Cardinal Alojzije Stepinac, Croatia's World War II primate whom John Paul beatified during a 1998 trip.

Stepinac was hailed as a hero by Catholics for his resistance to communism and refusal to separate the Croatian church from the Vatican. But his beatification was controversial because many Serbs and Jews accuse him of sympathizing with the Nazis.

On Saturday en route to Zagreb, Benedict praised Stepinac as a model for having defended "true humanism" against both the communists and the Ustasha Nazi puppet regime that ruled Croatia during the war. The Ustasha, said the German-born pope, "seemed to fulfill the dream of autonomy and independence, but in reality it was an autonomy that was a lie because it was used by Hitler for his aims."