Yesterday's launch -- the first this year -- came just days after the North's leader Kim Jong-Un said that he was open to the "highest-level" talks with Seoul.
"We launched some 300,000 leaflets last night", Lee Min-Bok, a North Korean defector who now heads the Campaign for Helping North Koreans, told AFP.
In October last year, Lee's balloons sparked a brief exchange of heavy machine gun fire across the border when the North attempted to shoot them down.
Pyongyang -- which refers to the activists as "human scum" -- has long condemned the leaflet launches, asking that they be banned.
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In his New Year's message, Kim also made it clear the South must stop criticising his regime.
However, a South Korean Unification Ministry official today reaffirmed the South's position that there is no legal basis for a blanket ban on leaflet launches.
"If we depart from the basic principle concerning the leaflet launches merely to resume dialogue, it would be undesirable for the development of normal South-North relations" in the long term, the official was quoted as saying by Yonhap news agency.
Police officers were deployed at the launch site Monday but did not intervene as the activists released the balloons.