UN special rapporteurs voiced concerns that South Korea's anti-leafleting law could restrict freedom of expression in a letter sent to the government calling for further clarification, the UN website showed Thursday.

Tomas Ojea Quintana, special rapporteur on North Korea's human rights situation, along with three other rapporteurs, made the appeal in a "communications" letter dated Monday, urging the South Korean government to provide additional information about the compliance of the anti-leafleting ban with international human rights law.

"We are concerned that this legislative amendment, due to its vague wording, may be interpreted broadly, and that its application may lead to the disproportionate penalisation of some forms of political expression and legitimate activities of some civil society actors in the ROK," they wrote, using the acronym for South Korea's official name, the Republic of Korea.

The rapporteurs expressed concerns that the anti-leafleting ban may "negatively impact the enjoyment of the right to freedom of expression" and the "legitimate activities" of nongovernmental organizations in Seoul.

Critics say the amendment to the Development of Inter-Korean Relations Act, which went into effect last month, could undercut efforts to send information into the reclusive North.

South Korea has stressed that the leafleting ban is necessary to protect the lives and safety of residents living in the border areas as such leaflets could provoke the North to take bellicose action.

The law prohibits the launching of anti-Pyongyang leaflets across the border, with violators subject to a maximum prison term of three years or a fine of 30 million won ($27,400). (Yonhap)