“The enemy king has appeared at the center of our nation!” the Rev. Song Choon-gil, a Presbyterian pastor, shouted during a rally of hundreds of Protestants who gathered a few blocks from the papal Mass on Saturday. Accompanied by a band, the evangelical Protestants sang hymns and danced, shouting that they were sounding “the trumpets of spiritual war” against the “idol worship” and “satanic forces” they said Roman Catholicism represents.

Although tensions between South Korea’s Catholics and Protestants are not new, the pope’s visit has brought into focus the often ugly rivalry between churches vying for hearts and souls in South Korea. It also comes as the country is still reeling from accusations by prosecutors that the pastor of a relatively small Christian church siphoned money from the company whose ferry sank in April, killing more than 200 teenagers.

The broader Protestant community has officially welcomed Francis’s visit, the first by a pope to the country in 25 years, and the pope planned to meet the country’s religious leaders on Monday to promote harmony among different faiths. But even many mainstream Protestants feel unsettled by the trip, which comes as some denominations are suffering image problems and stagnating membership after decades of explosive growth.

“What is interesting is that there is very little mention of the pope’s visit to Korea in Protestant media, even though it is the biggest news in the country right now,” said Koo Se-woong, an expert on Korean religions. “That silence itself speaks to the resentment Protestants feel toward the Catholic Church, which enjoys a greater level of public trust than the Protestant side.”

Catholics first brought Christianity to Korea more than two centuries ago. But Protestant churches pursued aggressive evangelism, especially in the 1970s and 1980s when they reached out to the millions of people who migrated to cities during a period of rapid industrialization. The country is now home to some of the largest megachurches in the world, all of them Protestant, including Yoido Full Gospel Church in Seoul, the world’s largest, with a congregation of more than 800,000.