Hundreds of thousands of South Korean Christians demonstrated in Seoul on Sunday to protest a court ruling that would allow same-sex couples to receive insurance from the National Health Insurance Service (NHIS).

The NHIS is South Korea’s single-payer government healthcare system. In July, the South Korean Supreme Court ruled that same-sex couples can register their partners as dependents.

This effectively elevated same-sex couples to the same status as common-law marriage, although the Supreme Court ruling — and the appeals court ruling it upheld — both took pains to maintain a distinction between marriage and same-sex relationships.

LGBTQ groups hailed the Supreme Court ruling as a step toward the inevitable recognition of same-sex marriage. According to polling company Gallup Korea, only about 17 percent of South Koreans favored legalizing gay marriage in 2000, but 40 percent are in favor today.

Hundreds of thousands of people from South Korean Christian groups held a massive prayer service in Seoul on Sunday to protest the Supreme Court ruling. Supporters of the event described it as one of the largest religious gatherings in South Korea’s history.

There was some dispute over the crowd size, with police estimating about 230,000, while the event organizers said there were over a million participants. The organizers claimed a million more people watched the prayer service as it was broadcast live on television.

The crowd was undeniably massive, spilling out of Seoul Plaza and other large venues to block traffic in the capital city. In addition to protesting the July Supreme Court decision, participants also voiced their opposition to a national anti-discrimination ordinance that has been proposed in various forms since 2011.

“Let the people discern how dangerous and totalitarian the fantasy of achieving equality by everyone being the same – instead of all being equal before God – is. So that such antihuman law that depresses freedom of the most people would not be passed,” said one of the prayers suggested by the organizations, an ad hoc committee including groups like the United Christian Churches of Korea and the Council of Presbyterian Churches in Korea.

The organizations denounced the anti-discrimination ordinance as a violation of “the law of nature and order in which the world was created,” and a threat to freedom of speech and conscience if it were ever passed.

The demonstrators further said they were opposed to a “student rights ordinance” adopted in several districts across Korea because they said it was “encouraging romantic relations between students of the same sex and leading to sexual humiliation.”

Speakers at the rally said the student rights ordinance, and the Supreme Court decision on the health insurance case, were efforts to impose same-sex marriage without due constitutional process because they would force the South Korean legal system to recognize same-sex unions as functionally equivalent to marriage.

“We see this not simply as a Christian issue, but as a huge crisis that shakes our country’s foundation,” said Kim Jeong-hee, a spokesperson for the organizers.

Some speakers alluded to South Korea’s dire demographic crisis, caused by one of the lowest birth rates in the world, as a reason to preserve marriage traditions for opposite-sex couples.

“Women’s rights are important, but it’s not just the women’s rights that are important. God wants a union between a man and a woman for a healthy family,” said Rev. Kim Yang-jae of Christian medicine group QTM.

Some Christian groups were opposed to the Seoul demonstration and its message, denouncing the event as “brainwashing” and circulating their own list of politicized prayer suggestions.

“Empower the pastors who bless sexual minorities and members of the congregation, which respects them as who they are,” said one of the alternative prayer suggestions.