TOKYO — Yes, North Korea has Catholics. It even has a Catholic church.

But while Pope Francis was welcomed by millions of South Korean Catholics last week, Christianity has largely been quashed north of the border and, as a string of recent arrests suggest, would-be missionaries there face severe risks amid a North-South religious divide that is perhaps wider than ever.

The church in North Korea is under tight government control and is not recognized by the Vatican. Indeed, services there would be hardly recognizable as Catholic to outsiders.

Inside North Korea’s one cathedral are crosses, but no crucifixes. Weekly services feature hymns and prayers offered in a highly formalized manner, but there are no sacraments. Nor are there priests: State-appointed laymen officiate services.

Officials in Pyongyang had no comment on Francis’ five-day South Korea visit. North Korea rejected an invitation to join in a peace and reconciliation Mass that Francis celebrated in Seoul. The North declined the invitation not on religious grounds, but with complaints about South Korea’s participation in military exercises with the United States.

“We feel deeply sorry about the outcome but we will continue to pray for another chance to celebrate the holy Mass with the North Korean faithful,” Vatican spokesman the Rev. Federico Lombardi said.

Compared with South Korea, where there are more than 5 million Catholics, estimates of the size of the North Korean Catholic flock range from 800 to about 3,000.

The lower estimates come from the United Nations Human Rights Commission, which recently cited the lack of religious freedom in the North as one example of its poor human rights record. The higher estimate comes from the Korean Catholic Association, a North Korean government-controlled body that is responsible for all official information about the church and coordinates a weekly service for followers.

Before the advent of the North Korean regime, Pyongyang had more Christians than any other city in Korea and was known as the “Korean Jerusalem.” Seen as fertile ground for missionary work, Pyongyang also had a seated bishop.

Most of that presence was erased by the early 1950s, and the North has kept a tight lid on all Christian activities since. No Holy See-sanctioned church institutions or priests operate in North Korea, and the country’s one Catholic church, the Changchung Cathedral in Pyongyang, is not supported by the Vatican.

Son Jung-hun, a 49-year-old human rights activist in Seoul who was born and raised in Pyongyang before defecting to the South at age 35, said regular people in Pyongyang cannot go to the Catholic church and participate in services.

“The Catholics in Pyongyang would not know about the pope’s visit to South Korea, the history of South Korean Catholicism and the significance of the pope’s visit,” Son said. “Senior government officials who work in foreign affairs and others know about the pope’s visit, but average citizens will never know.”

Being a Catholic, per se, is not illegal. Article 14 of the 1948 constitution states that citizens “shall have the freedom of religious belief and of conducting religious services.” But because the ideals of Christianity — and the worship of Jesus — are not in line with North Korea’s rigorously enforced political ideology, believers are considered suspect. The same is true for most religious groups, but Christianity is seen as a larger threat.

Lionel Jensen, an associate professor of East Asian Languages and Cultures at the University of Notre Dame, said: “If news of the papal visit to Seoul has gotten out to the people of North Korea, I can only speculate that the quiet Catholics among them would be enthused. My best sense is that there is cognizance of the visit but very few would be willing to speak publicly about this.”

The North has recently taken a hard line on foreigners allegedly trying to spread Christianity.

Korean-American missionary Kenneth Bae has been held since November 2012 and is serving 15 years of hard labor for what North Korea says were hostile acts against the state. In March, it deported an Australian missionary. American Jeffrey Fowle is now being detained for allegedly leaving a Bible in a nightclub in the northern port city of Chongjin.

In May, North Korea sentenced a South Korean Baptist missionary to hard labor for life for allegedly spying and trying to set up underground churches.

“Pray for our brothers in the North,” Francis said Friday, as he led several thousand young Catholics in South Korea in a moment of silent prayer for unification.