SEOUL, South Korea — Pope Francis beatified 124 Korean martyrs on Saturday, telling hundreds of thousands of people who turned out for his open-air Mass that their ancestors’ willingness to die rather than renounce their faith two centuries ago was a model for Asian missionaries today.

The streets leading up to Seoul’s iconic Gwanghwamun Gate were packed with Koreans honoring the lay Catholics who founded the church here in the 18th century. Korea’s church is unique in that it was founded not by foreign missionary priests — as occurred in most of the world — but by members of Korea’s own noble classes who learned of Christianity by reading books about it.

These early Catholics were killed in the 18th and 19th centuries by the Joseon Dynasty, which tried to shut the Korean Peninsula off from Western influence.

Police in Seoul declined to give an estimate of the crowd size, but the Vatican said about 800,000 people had turned out. The number was significant given that Catholics represent only about 10 percent of South Korea’s 50 million people.

The Mass kicked off a busy day for Francis as he passed the halfway mark of his five-day South Korea visit.