All passengers flying from Indonesia, including South Koreans, must now present a negative COVID-19 polymerase chain reaction(PCR) test result to board flights to South Korea. 

The Central Disaster and Safety Countermeasures Headquarters announced the measure on Sunday, effective immediately, to respond to the highly transmissible Delta variant.

The move comes as the number of confirmed cases among incoming passengers from Indonesia came to 240 in the past four weeks, including 132 Korean nationals. 

Authorities are on high alert over arrivals from Indoensia as the Delta variant is spreading rapidly in the Southeast Asian country. The Red Cross warned last week that "Indonesia teeters on the edge of a COVID-19 catastrophe."