The number of confirmed coronavirus cases in South Korea has doubled in one day, with the majority linked to the worshipper of a mysterious “cult” church known as Patient 31.

Despite Daegu, the country’s fourth largest city, being placed on lockdown – and its 2.5 million residents told to stay indoors as heavily-clad workers disinfect the streets – the number of known patients leapt to 433 after 239 new cases were discovered on Saturday.

Officials warned the tally would likely continue to rise significantly, with more than 1,000 people who attended religious services at a Daegu branch of the Shincheonji Church of Jesus reporting symptoms.

Korea’s Centres for Disease Control and Prevention (KCDC) has designated Daegu and Cheongdo county – where more than 100 cases have been confirmed at a hospital’s psychiatric ward – as “special care zones”, sending military medical staff, other health workers and extra resources.

More than half of the country’s cases are linked to a 61-year-old woman known as Patient 31, who before her diagnosis attended at least four services at the Temple of the Tabernacle of the Testimony, a Daegu church whose leader claims to be the returned Jesus Christ.

'A zombie apocalypse': Daegu on lockdown - in pictures Show all 10 1 /10 'A zombie apocalypse': Daegu on lockdown - in pictures 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu The near-deserted streets of Daegu's Dongseongro shopping district AFP via Getty Images 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu People line up to buy foods and supplies at a supermarket in Daegu AP 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu A beggar wearing a mask to prevent contracting the coronavirus is pictured on Dongseongro shopping street REUTERS 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu Shopkeepers on Dongseongro shopping street in central Daegu REUTERS 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu Women wearing masks in Daegu's Dongseongro shopping district REUTERS 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu Medical workers wearing protective gear transfer a suspected coronavirus patient (C) to hospital YONHAP/AFP via Getty Images 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu South Korean health officials spray disinfectant in front of the Daegu branch of the Shincheonji Church of Jesus AFP via Getty Images 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu South Korean health officials spray disinfectant AFP via Getty Images 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu A South Korean man wears a protection mask while walking in central Daegu EPA 'A zombie apocalypse': Daegu on lockdown - in pictures Coronavirus outbreak in Daegu A South Korean health official sprays disinfectant front of a hospital YONHAP/AFP via Getty Images

She had no recent record of overseas travel, authorities said, and local media reported that after developing a fever on 10 Feburary she twice refused to be tested for the coronavirus due to having not recently travelled abroad.

KCDC said on Saturday it had obtained a list of 9,300 people who had attended church services, around 1,200 of whom had complained of flu-like symptoms.

“We are conducting investigation based on the database ... we have obtained,” KCDC director Jeong Eun-kyeong said, while Daegu’s mayor added all believers of the church would be tested and have been asked to self-isolate at home, away from their families.

South Korean president Moon Jae-in has also ordered an investigation into whether the outbreaks at the church and hospital – home to more than 114 cases, the vast majority in its psychiatric unit – are linked.

“We think the patients had repeated exposure given the isolated facility of the psychiatric wards, where many patients share the same room,” the KCDC’s Mr Jeong told reporters.

Earlier this month, several of the church’s followers visited the hospital to attend a funeral for the brother of the church’s founder Lee Man-hee.

Mr Lee claims to be the second coming of Christ and promises to take 144,000 people with him to heaven on Judgement Day. Shincheonji followers reportedly believe Mr Lee is immortal, and according to the church’s teachings only he can interpret and understand the bible’s true meaning.

The Shincheonji church said it has closed all of its 74 sanctuaries in South Korea and told followers to instead watch its services on YouTube.

“We are deeply sorry that because of one of our members, who thought of her condition as a cold because she had not travelled abroad, led to many in our church being infected and thereby caused concern to the local community,” the church said in a statement.

Two Covid-19 patients have now died in South Korea, both at the Cheongdo hospital. One was a woman in her fifties who was transferred from the country’s second largest city, Busan, for treatment, and a 63-year-old man.

In the capital of Seoul, thousands took to the streets on Saturday for regular weekend political rallies, despite the city’s mayor saying the gatherings would be banned as part of containment measures. Seoul police told Reuters they were aware of the ban but that it would be an “abuse of power” for them to intervene.

Workers wearing protective gears spray disinfectant on Daegu's deserted streets (Kim Jun-beom/Yonhap via AP)

The country is now home to the largest outbreak outside of China and the Diamond Princess cruise ship, where more than 600 passengers became infected as it was quarantined off the shore of Japan.

A repatriation flight carrying Britons and Europeans who had been held aboard the cruise ship landed in the UK on Saturday, where they will face a two-week quarantine in the Wirral’s Arrowe Park Hospital. Several UK nationals infected with the virus remain hospitalised in Japan.

The death toll from the outbreak in mainland China rose to 2,345 as of Friday with more than 76,000 people infected.

Meanwhile, new clusters of infection in South Korea, Singapore and Iran led some experts to suggest the virus may be nearing the level of a pandemic.

The World Health Organisation (WHO) has lauded China’s containment efforts as buying time for the rest of the world to prepare.

But the emergence of hot spots around the globe – and trouble finding the the first patients who have sparked each new cluster – might signal the disease has begun spreading too widely for tried-and-true public health steps to stamp it out.

“A number of spot fires, occurring around the world is a sign that things are ticking along, and what we are going to have here is probably a pandemic,” said Ian Mackay, who studies viruses at Australia’s University of Queensland.

The WHO defines a “global pandemic” as a disease spreading on two continents, though some public health experts would call an outbreak a pandemic if the spread is over a wide area or across many international borders.