President Donald Trump and North Korea are locked in a war of words and South Koreans fear that the tensions could turn into an actual war. Videos of South Koreans preparing survivals kits are going viral amidst the backdrop of North Korea calling Trump’s tweets a declaration of war.

“Just heard Foreign Minister of North Korea speak at U.N. If he echoes thoughts of Little Rocket Man, they won't be around much longer!” tweeted Trump on Saturday.

North Korea's Foreign Minister Ri Yong Ho replied to Trump on Monday in New York.

“Since the United States declared war on our country, we will have every right to make all self-defensive countermeasures, including the right to shoot down the United States strategic bombers at any time even when they are not yet inside the aerospace border of our country,” said Ri.

The videos show people packing the essentials that might be needed in the event of a nuclear war: food, water, gas masks and clothes.

South Korea’s capital, Seoul, is home to nearly 10 million people and is less than 40 miles from the North Korean border. North Korea has many conventional weapons along the border with South Korea, called the demilitarized zone, including missiles and artillery all aimed at South Korea. The new fear, however, is North Korea’s ability to launch a nuclear weapon at South Korea. At the beginning this month, North Korea tested their most powerful nuclear weapon yet and claimed it to be a hydrogen bomb.

North Korea also tested two intercontinental ballistic missiles in July, weapons that have the theoretical range of hitting the continental U.S. North Korea had successfully developed miniaturized nuclear weapons that could be outfitted on a missile’s warhead according to U.S. intelligence.

North Korea isn’t afraid of being provocative with its tests and launched two missiles this year that flew directly over Japan. North Korea has long been known for its blustery rhetoric, but now have an equally bellicose sparring partner in Trump.

In his speech to the United Nations (U.N.) General Assembly last week, Trump called North Korea’s leader Kim Jong Un the insult “Rocket Man” and threatened to “totally destroy” his country. Kim responded by calling Trump what was translated as “a dotard,” which is a senile old person.

The U.S. flew bombers as far north as they’ve gone above the demilitarized zone this century over the weekend as a show of force. The U.N. Security Council ratcheted up economic sanctions on the country as well this year in an attempt force North Korea to slow down or give up their nuclear program.