Pope Francis has pressed his call for Sri Lankan reconciliation by canonising the country's first saint as a model for national unity and visiting the war-ravaged north to pray at a shrine revered by both Sinhalese and Tamil faithful.

More than a half-million people packed the capital's seafront park for the Mass, with some spending the night under the stars to ensure a good spot. Seemingly rested after a gruelling first day of his Asian tour, Francis arrived well ahead of time to greet the crowd, leaving his "popemobile" to kiss the sick and handicapped.

Bells rang out and the crowd erupted in applause when Francis declared the Rev Joseph Vaz a saint at the start of the service. The 17th-century Indian missionary revived the faith in Sri Lanka during a time of anti-Catholic persecution by Dutch colonists, who were Protestant Calvinists.

The Catholic Church considers Vaz a great model for today, ministering to both Sri Lanka's main ethnic groups and putting himself at great risk to spread the faith.

Francis told the crowd that Vaz lived at a time - like today - when Catholics were a minority and often persecuted, and yet he ministered to all, regardless of their ethnic or religious background.

"St Joseph shows us the importance of transcending religious divisions in the service of peace," Francis said in his homily, delivered in English and then translated for the crowd in both Sinhalese and Tamil.

"As the life of St Joseph Vaz teaches us, genuine worship of God bears fruit not in discrimination, hatred and violence, but in respect for the sacredness of life, respect for the dignity and freedom of others, and loving commitment to the welfare of all."

He said the Sri Lankan church today only wanted to continue Vaz's legacy of service to all, asking only for the freedom to preach in return. "Religious freedom is a fundamental human right," he said.

To underscore that point, the Pope gave Sri Lanka's bishops a replica of a 17th-century decree from the then king of Kandy allowing Catholic conversions of Buddhists - a somewhat provocative message given the recent upswing in violence against Muslims and some Protestant churches by Buddhist extremists who want Sri Lanka exclusively Buddhist.

After Mass, Francis headed by helicopter to the northern city of Madhu to pray at the Our Lady of Madhu shrine, a Catholic pilgrimage site that is a destination for people of other faiths as well. The visit is the first by a pope to the northern Tamil territory that was devastated by Sri Lanka's 25-year civil war, which erupted with Tamil demands for an independent homeland because of perceived discrimination by the Sinhalese majority.

He is expected to call again for reconciliation between Sinhalese and Tamils, and people of different faiths, to overcome the wounds of the war.

Upon his arrival in Sri Lanka yesteday, Francis called for reconciliation but also for the truth to come about injustices committed during the conflict, which ended in 2009 with the army's violent crushing of the Tamil Tiger rebels.

Catholics make up slightly more than 6% of Sri Lanka's population of 21 million. They are by far the largest Christian denomination in the country, but are a distinct minority compared to Buddhists, who make up about 70%, with Hindus comprising 13%. Muslims make up about 10% of the population.

Most Sinhalese are Buddhist and most Tamils Hindu, but the Catholic Church counts both ethnic groups as its members, and as a result considers itself a source of unity for the country.

Today's Mass drew people from across the teardrop-shaped Indian Ocean island nation, eager to see the first pope to visit since St. John Paul II in 1995. In fact, it was during that brief visit that John Paul beatified Vaz, using the same altar that Francis used to make Vaz a saint.

The crowds poured off buses and out into the street from the nearby railway station. Security was tight and everyone had to walk the last few hundred yards to the Galle Face Green, but the atmosphere was festive and ordered. Taxi drivers handed out free cups of tea and the crowd was treated to traditional dancing and music.

The park has a capacity of 500,000 and Vatican spokesman the Rev Federico Lombardi, said the crowd more than surpassed the half-million mark.

"My son can't understand what's going on, but I will take photographs and show him when he grows up how he attended this Holy Mass," Pradeep Niroshan, a 31-year-old insurance agent, said as he carried his two-year-old son to the service.

"It will be memorable for him, because the next pope to come to Sri Lanka may be after 20 years."

Tomorrow Francis flies to the Philippines for the second and final leg of his Asian pilgrimage.