Pope Francis has beatified 124 Korean martyrs in the key event of his five-day visit to East Asia. Hundreds of thousands turned up to commemorate Christians killed during the church's early years on the peninsula.
There was a collective cheer when Francis declared the 124 "blessed" - the first step toward possible sainthood - during the Saturday ceremony.
Streets around Seoul's Gwanghwamun Gate were filled with Koreans honoring the early Catholics who were killed in the 18th and 19th centuries. While police declined to give the exact number of people attending, local media put the figure at about a million.
Francis paid tribute to the dead, claiming that the concept of martyrdom was important for Christians to recognize.
"They knew the cost of discipleship ... and were willing to make great sacrifices," the pope said. "They challenge us to think about what, if anything, we ourselves would be willing to die for."
The deaths of the Christians - adherents of the 18th century nobleman, Paul Yun Ji-Chung - were part of the wider persecution of the Church by the Joseon Dynasty, as it tried to shut Korea off from Western influences and ideas. According to the Vatican, about 10,000 Koreans were martyred in the first 100 years after Catholicism was introduced to Korea.
There was a stunning backdrop to the event, which took place in front of the Gyeongbokgung palace and the presidential Blue House.
Seoul faithful show appreciation
Francis had been led through the crowds in an open-topped vehicle, from which he saluted and blessed followers.
Earlier, the pontiff baptized a man who converted to Catholicism after losing his son in the South Korean ferry disaster in April. He also visited a large Catholic-run center in Eumseong, some 100 kilometres (about 60 miles) south-east of Seoul.
Since he arrived on Thursday, Francis has met several families of victims of the April ferry disaster, as well as South Korean President Park Geun Hye. Among the key themes of his visit have been the wealth gap between rich and poor and the need for peace on the divided peninsula.
rc/av (AP, AFP, dpa)