The government staged a nationwide civil defense drill Wednesday against possible attacks by North Korea as cross-border tensions run high after the North's shelling of a border island last month.
The exercise began at 2 p.m. with all South Koreans asked to flee to nearby air raid shelters, subway stations or other designated underground facilities at the sound of the raid sirens.
Ten mock North Korean aircraft flew over major cities, including Seoul and Busan, and people driving cars were asked to immediately park along roads and go to shelters.
The 15-minute drill was the largest-ever in the country since such drills began in 1975, according to the National Emergency Management Agency.
South Korea, which remains technically at war with the North because the 1950-53 Korean War ended in a truce, not a peace treaty, has been conducting the drills eight times a year. However, they were often largely ignored and not complied with fully by the public.
"This is the first time since 2000 that mock enemy aircraft are flown and drivers are asked to park their cars and evacuate to safety during a drill," said Choi Hong-yeong, a publicity official at the agency.
"Overall, it is the largest drill since 1975," he added.
Passengers at seven subway stations in the capital learned how to use gas masks during a special evacuation drill.
In border areas with the North, public officials received training against North Korea's chemical, biological and radiological attacks.
Some citizens were still disobedient, with drivers caught by the siren in the congested Gwanghwamun intersection of central Seoul sitting out the entire drill inside their cars.
Flights and ferries operated normally. Trains and vehicles on highways were asked to slow down for the first three minutes of the drill.
Also exempt from the drill were areas hit by the foot-and-mouth disease, such as North Gyeongsang Province, Yeoncheon and Yangju, officials said.
The drill was held as tensions run high on the Korean Peninsula following the North's Nov. 23 artillery attack on Yeonpyeong Island near the tense Yellow Sea border that killed four people.
The bombardment also injured 18 people and destroyed dozens of homes, marking the first attack by the North on a civilian area on the South's soil since the end of the Korean War.