South Korean activists have launched an anti-North Korea balloon campaign, sending packages containing leaflets, USB drives and money across the border, despite the North's government threatening to target the "human scum" involved.

The balloons started floating over the border on Wednesday containing US dollar bills, DVDs detailing human rights abuses in North, and transistor radios.

"There is clearly enormous hunger for outside information in North Korea," said Thor Halvorssen, the president of the US-based Human Rights Foundation, which supported the event in the border town of Paju.

"USB keys are one of the most powerful tools, because they're small, can be hidden and shared easily, and carry massive amounts of data."

Each of the 1,500 USB drives were loaded with the Korean-language version of Wikipedia.

The balloon launch was organised by a defector group, Fighters for a Free North Korea.

"This is aimed at letting North Korean people know about [leader] Kim Jong-Un's brutality...and deliver a message to North Koreans that now is time for them to rise up and finish the dictatorship," said the group's leader Park Sang-Hak.

South Korean police have enforced bans on similar launches in the past, citing concerns from local residents about possible North Korean retaliation.

Last October, in response to a balloon launch, a statement from the North's Secretariat of the Committee for the Peaceful Reunification of Korea said: "This is another intolerable challenge to the DPRK [North Korea].

"We will never tolerate the foolish act of the puppet warmongers but wipe out the provokers with merciless firing.

"We will deal a telling blow at the [South Korean] army to make it pay a very high price for its foolish provocation as it is keen on staging 'psychological warfare against the North' in alignment with human scum," said the statement, which was carried by the country's official news agency.