South Korea stages its largest ever civil defence drill as tensions mount on the Korean peninsula.
South Korea is preparing for the worst.
On Wednesday the nation staged its largest-ever civil defence drill in preparation for a possible North Korean attack.
In the heart of Seoul, a warning siren sounded to signal the start of the drill.
Drivers stopped their vehicles on the roads, and pedestrians made their way into a subway shelter.
Students went through the sequence of an evacuation, donning masks to protect against gas and smoke and taking refuge underground.
South Korea's Prime Minister Kim Hwang-sik watched the drill from a tower in Seoul.
"To be prepared against North Korea's surprise attacks, all citizens should make themselves familiar with what they must do during the attacks. So we are holding this drill in ordinary times."
In Paju, near the North Korean border, residents of an apartment complex staged an anti-biochemical exercise.
Tensions on the Peninsula are at their highest in decades.
In March North Korea's sinking of the South Korean ship the Cheonan killed 46 sailors.
More recently Pyongyang fired artillery shells at Yeonpyeong Island in November, killing four people including two civilians.
North and South Korea are still technically at war since the 1950-53 Korean War with about one million troops at their respective sides of the Demilitarised zone separating them.
Maryam Ishani, Reuters.