A South Korean Internet newspaper says that North Korean authorities have been on alert since graffiti denouncing North Korean leader Kim Jong-il was found in Pyongyang.

The Daily NK reported that the graffiti was written last Friday in white chalk on a red brick wall of the Pyongyang College of Railways. The graffiti said former South Korean president Park Chung-hee was a dictator that developed his country’s economy and North Korean leader Kim is a dictator who has starved his people to death.

The Daily NK said immediately after finding the graffiti, North Korean authorities organized a joint investigation team comprised of the National Security Agency and People’s Safety Ministry. The South Korean medium reported that North Korean authorities suspended railroad operations in Pyongyang for three days from Monday, and questioned students of the college and visitors to Pyongyang.