Ten activists in the Imjingak park near the border sent 10 helium balloons containing 200,000 leaflets that denounce the ruling Kim family for staging a costly rocket launch while its people starve, an AFP reporter saw.
In the week-long lead up to the April 15 centenary of the birth of Kim Il-Sung, which culminated in a massive military parade on Sunday, the North launched what it claimed was a satellite-carrying rocket.
The launch on Friday, estimated by Seoul to have cost the North about $850 million, failed after the rocket exploded about two minutes after blast-off.
The US and South Korea view it as a disguised long-range missile banned under UN resolutions.
"The spending for the launch could have fed 20 million people (in the North) for an entire year" read a banner attached to a giant balloon, which also contained a thousand $1 dollar bills.
"The nation's three top traitors: Kim Il-Sung, Kim Jong-Il, Kim Jong-Un" read another banner, referring to the North's previous and current leaders, while another stated: "Let's exterminate Kim Jong-Un's dictatorship".
Jong-Un took over from his late father and longtime ruler, Kim Jong-Il, after his death last December.
The young leader has practically assumed all the top party, military and state posts previously held by his father, who had also taken over from his own father in 1994, completing the three-generation power succession.
Last week he was appointed as the "first secretary" of the ruling Workers' Party and "first chairman" of the powerful National Defense Commission, the nation's top decision-making body.
Jong-Un, believed to be in his late 20s, also delivered his first public speech to tens of thousands of cheering troops and people during the military parade in the capital Pyongyang.
The isolated North, which tightly controls news from outside, has angrily responded to past balloon launches and threatened to fire across the heavily-fortified border to stop them.