South Korea is raising its alert on the new coronavirus to the "highest level", President Moon Jae-in said Sunday, as the country reported 123 new infections.
South Korea has seen a rapid surge in the number of coronavirus cases in recent days after a cluster of infections emerged from a religious sect in the southern city of Daegu last week.
The national toll of 556 cases is now the highest outside China, apart from the Diamond Princess cruise ship in Japan.
"The COVID-19 incident faces a grave turning point. The next few days will be crucial," Moon said following a government meeting on the virus.
"The government will raise the alert level to the highest level of 'grave' according to experts' recommendations and drastically strengthen our response system," President Moon said. He also urged officials not to hesitate from taking "unprecedented powerful measures" to contain the outbreak.
On Sunday, South Korea reported 123 new cases and two deaths, taking the countrywide toll to four.
One of the victims was a patient being treated for mental health issues at a hospital in Cheongdo, a southern city linked to the religious sect where around 100 new cases were reported.
Among the latest infections, 75 involved the Shincheonji Church of Jesus in the nearby city of Daegu, the Korea Centers for Disease Control and Prevention said.
More than 300 cases have been linked to the church, starting with a 61-year-old woman who developed a fever on February 10 and attended at least four church services in Daegu before being diagnosed.
Some 9,300 Shincheonji members in Daegu have either been quarantined or have been asked to stay at home, said KCDC director Jung Eun-kyeong, with more than 1,240 saying they had symptoms.
Daegu -- South Korea's fourth-biggest city, with a population of 2.5 million -- reported more than 90 new cases on Sunday, bringing the city's total to 247, mayor Kwon Young-jin said.
"The crisis level of Daegu and the North Gyeongsang province is grave," said Kwon Young-jin, who advised locals to stay indoors.
The mayor asked all Shincheonji members with symptoms to come forward and be tested. Authorities have yet to reach around 670 members of the church.
Shincheonji is often accused of being a cult, and claims its founder has donned the mantle of Jesus Christ and will take 144,000 people with him to heaven on judgement day.
But with more church members than available places in heaven, they are said to have to compete for slots and pursue converts.
"Hiding is not the answer. If you hide, it could hurt your health, your family's health, and will not help in the early cessation of the situation," Kwon said.
Daegu and Cheongdo -- the birthplace of Shincheonji's founder Lee Man-hee -- were designated as "special management zones" on Friday.
Among the new cases were 18 people who recently returned from a group pilgrimage to Israel, the KCDC said.
It was unclear how they had contracted the infection, but authorities said one of the victims were likely exposed to the virus before their trip, given Israel has reported only one confirmed COVID-19 case so far.
Israel has issued an entry ban on South Koreans and refused to allow non-Israelis to disembark from a Korean Air plane on Saturday.
The US State Department on Saturday raised its travel advisory for South Korea, joining a handful of countries bolstering their vigilance after its rapid spike in the number of infections.
US citizens were asked to "exercise increased caution" when travelling to South Korea, where "sustained community spread" has been reported.
"Sustained community spread means that people in South Korea have been infected with the virus, but how or where they became infected is not known, and the spread is ongoing," the State Department said on its website.
Separately, the US Centers for Disease Control and Prevention also issued an "Alert Level 2" travel health notice, saying "older adults and those with chronic medical conditions should consider postponing nonessential travel".
Britain has also advised its nationals "against all but essential travel to Daegu and Cheongdo".
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