The controversial religious group at the heart of South Korea's coronavirus crisis had meetings in the now quarantined Chinese city of Wuhan until mid-December, according to new reports.

The development has escalated fears that the Shincheonji church disease cluster could extend across international borders.

More than half of the almost 1,300 confirmed coronavirus cases in South Korea have been linked to Shincheonji's branch in Daegu, a city of 2.5 million people. They may be connected to a possible "super spreader", known as "patient 31", who attended four February services.

On Wednesday, the Hong Kong-based South China Morning Post reported that members of the secretive group had held meetings in Wuhan, the original Covid-19 epicentre, until December.

"Rumours about a virus began to circulate in November, but no one took them seriously," one Shincheonji church member, a 28-year-old kindergarten teacher, told the paper.

"I was in Wuhan in December when our church suspended all gatherings as soon as we learned about it [the coronavirus]," she added, saying most members had returned home at the start of the Lunar New Year holiday late last month.