Park Sang-hak appears at the Seoul Metropolitan Police Agency in Seoul, Tuesday. Yonhap

Police on Tuesday called in the head of a North Korean defector group over its anti-Pyongyang leafleting campaign, which Seoul views as a breach of law and Pyongyang vehemently criticizes.

Park Sang-hak, head of Fighters for a Free North Korea, showed up for questioning at the Seoul Metropolitan Police Agency at 9:30 a.m. The former defector is known to have scheduled his attendance in advance with authorities.

Defying the government's warning against leafleting, Park claimed that his group sent some 500,000 leaflets carried by 20 large helium balloons over to the North on Monday last week.

Cheong Wa Dae earlier warned that the government would crack down on such acts, which it said constitute a violation of laws including the inter-Korean exchange and cooperation act.

The campaign to scatter leaflets that criticize the North Korean political system and the North's ruling Kim family has recently been a major source of confrontation between the two Koreas.

Police plan to question him on various suspicions raised against his activist group that has been leading the leafleting campaign.

Last week, police raided the offices of the Seoul-based group as well as Kuensaem, another anti-North Korea activist group run by Park's younger brother.

They have also been probing into the case by interviewing residents in the border towns of Gimpo, Paju and Yeoncheon in Gyeonggi Province and Gangwha in Incheon, west of Seoul.

Police are expected to decide whether to push for Park's indictment following the questioning. (Yonhap)