Pope Francis has lauded the strength and religious fervour of Paraguayan women while visiting the country's most important pilgrimage site.

Thousands of his fellow Argentines joined hundreds of thousands of local faithful at the site to welcome Latin America's first pope.

"Being here with you makes me feel at home," Francis said in his homily. He then spoke affectionately about the women of this tiny, land-locked nation, praising them for rebuilding the country after a devastating war in the 1860s wiped out more than half the population, primarily men.

"Then and now, you found the strength not to let this land lose its bearings," he said to wild cheers from the crowd.

"God bless your perseverance. God bless and encourage your faith. God bless the women of Paraguay, the most glorious women of America."

Thousands of people packed the main square and nearby streets at Caacupe. Argentina's blue and white flag and its national team football jersey were ubiquitous among the mate tea-sipping faithful.

The gathering at the Sanctuary of the Virgin of Caacupe was evidence of Francis' special affection for the revered image of the Virgin Mary. He declared the simple church, which houses a little wooden statue of the virgin, the world's newest basilica.

When he was archbishop of Buenos Aires, the former Cardinal Jorge Mario Bergoglio often visited the Villa 21 slum where many Paraguayan immigrants live, joining them in their religious processions and celebrating baptisms at their church, Our Lady of Miracles of Caacupe.