He's calling for a "high-alert posture" against the "recent fast-changing" situation on the Korean Peninsula, KCNA said.
One outlet reports the North Korean leader has lost a "significant amount of weight".
Orphans, soldiers, students and children have apparently "volunteered" for coal mine and construction work.
He's pushing ahead with the plans despite international sanctions and an economic crisis.
Washington has been warned it might face "something that is not good" if the "thoughtless remarks" continue.
Kim Yo-jong has issued a stern warning to the US as President Biden prepares to set out his Korean policy.
It raises questions about how Biden will address mounting tensions with Pyongyang over its nuclear weapons.
They had to push the handcar through the border crossing which was more than 1km.
He has asked for asylum in South Korea.