SEOUL, South Korea — As South Korea struggles to contain a snowballing coronavirus outbreak, its president on Sunday raised the country’s alert level to the highest for the first time in a decade, which empowered the government to lock down cities, bar visitors from China and unilaterally restrict the movement of people.

In raising the alert level, President Moon Jae-in is effectively acknowledging that the virus is threatening to spin out of control, after the number of cases has jumped to 763 in a few days and the death toll has risen to six.

The world is closely watching South Korea, concerned that it has become another hot spot of infection outside China. Emerging outbreaks in South Korea, Iran and Italy have provoked fear that the epidemic could turn into a global pandemic, as countries impose more travel restrictions and containment measures.