South Korean activists have launched balloons carrying leaflets condemning Pyongyang across the border, an act that could derail fresh attempts to resume long-stalled dialogue between the two rivals.

Monday'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 news agency.

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.

The incident scuppered a planned resumption of high-level talks between the two Koreas.

Pyongyang - which refers to the activists as "human scum" - has long condemned the leaflet launches, asking that they be banned.

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 on Tuesday 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.

But South Korea has, at times of high cross-border tensions, urged activists to exercise common sense and restraint and police have prevented such launches, citing the possible dangers posed to local residents.

Sanctions 'appropriate'

Police officers were deployed at the launch site on Monday but did not intervene as the activists released the balloons.

Also on Monday, Seoul's Unification Ministry said that the US sanctions against North Korea were appropriate.

"As the foreign ministry already defined our government's stance in a statement, we see these sanctions as an appropriate action," said South Korean Unification Ministry spokesman Lim Byeong-cheol at a regular news briefing.

US President Barack Obama on Friday issued an executive order authorising expanded sanctions against North Korea in the wake of the hacking of Sony Pictures Entertainment, which Washington blamed on Pyongyang.

Washington named three entities, including North Korea's military intelligence agency, and sanctioned 10 people with links to weapons sales and proliferation.

North Korea on Sunday slammed the fresh US sanctions against it, calling them hostile and repressive policies by Washington. Pyongyang has denied involvement in the cyberattack.

Source: Agencies