Seoul (AFP) - South Korea reported 161 more coronavirus cases Monday, taking the nationwide total to 763 and making it the world's largest total outside China.

The country has seen a rapid surge in the number of coronavirus cases -- adding more than 700 cases in less than a week -- since a cluster of infections emerged from a religious sect in the southern city of Daegu.

Most of the country's cases are connected to the Shincheonji Church of Jesus in Daegu, including 129 of Monday's confirmations, the Korea Centers for Disease Control and Prevention said in a statement.

Two more people had died, it added -- both of them connected to a second cluster around a hospital -- taking the toll to seven.

More than 100 cases have been confirmed at the Daenam Hospital in Cheongdo, near Daegu, most of them inpatients being treated for mental illnesses.

South Korean President Moon Jae-in on Sunday raised the country's virus alert to the highest "red" level, in a bid to strengthen the government response to the spiralling outbreak.

The government has extended kindergarten and school holidays by one week nationwide and said it will enforce tougher restrictions on group events.

Health authorities will check about 28,000 people in Daegu -- South Korea's fourth-biggest city, with a population of 2.5 million -- and residents were asked to stay at home.

"Please minimise going outside for at least two weeks," vice health minister Kim Gang-lip urged them.

Korean Air said it had suspended all of its flights to Daegu until the end of March "due to the coronavirus", while Asiana Airlines said it would suspend its Daegu-Jeju route on Tuesday.

- 'Causing concern' -

The Shincheonji cluster began with a 61-year-old woman who developed a fever on February 10 and attended at least four services in Daegu before being diagnosed.

The city's mayor Kwon Young-jin said 85 percent of its 292 cases were linked to Shincheonji.

Authorities say some 9,300 Shincheonji members in Daegu have either been quarantined or have been asked to stay at home, but hundreds have still yet to be reached.

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Shincheonji, often accused of being a cult, 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.

Around 500,000 people have signed a petition on the website of the presidential Blue House demanded the dissolution of Shincheonji, blaming the outbreak on its "immoral doctrine".

In a video statement read out by its spokesman on Sunday, Shincheonji apologised for "causing concern", but insisted it was cooperating with health authorities for the "early cessation" of the situation.

The spokesman rejected public criticism, noting the virus had broken out in China.

"Please be aware that the Shincheonji Church of Jesus and its members are the biggest victims of the COVID-19," he said.

The outbreak forced South Korean tech giant Samsung Electronics to suspend operations at its smartphone plant in Gumi, 200 kilometres (125 miles) southeast of Seoul at the weekend after an employee was infected.

The Gumi plant manufactures high-end products for the domestic market, including Samsung's latest Galaxy S20 and luxury Galaxy Z Flip models.

South Korean broadcaster JTBC was forced to skip its morning news programme Monday after its weather forecaster showed symptoms, prompting all staff to be self-quarantined, according to Yonhap news agency.