South Korea and North Korea began firing rockets on each other this past Thursday, reported CBS News. North Korea fired a single rocket and South Korea responded by firing dozens of shells. The United Nations has yet to respond.

Tensions arose when Seoul accused North Korea of planting landmines in a demilitarized zone in South Korea that maimed two South Korean soldiers. For the first time in 11 years, South Korea has begun running anti-Pyongyang propaganda. North Korea has threatened attacks against the loudspeakers broadcasting the messages.

“Our military has stepped up monitoring and is closely watching North Korean military movements,” said the South Korean defense ministry.

North Korea is particularly sensitive to any sort of propaganda or criticism aimed at its leader, Kim Jong Un. Analysts say such sensitivity is derived from fear that such propaganda could “weaken Kim’s grip on absolute power.” Pro-Kim propaganda illustrates the North Korean leader as a god of sorts.

CBS News reported that occasional firing between North and South Korea is not uncommon. Last year, North Korean troops fired weapons into South Korea after activists launched balloons carrying anti-Pyongyang leaflets. However, North Korea’s army said South Korean propaganda is a declaration of war.