Seoul, Jul 17 (IANS): The South Korean Unification Ministry said on Friday that it revoked the operation permits of two North Korean defector groups over their sending of anti-Pyongyang propaganda leaflets.

The Ministry said it revoked the operation permits of Fighters for a Free North Korea and Kuensaem after comprehensively reviewing related documents, including their final say, reports Yonhap News Agency.

Sending leaflets and other items to North Korea jeopardizes the safety of residents in the border and creates tension in the Korean Peninsula, it added.

Losing operation permits would make it hard for the groups to raise money for their operations and activities, as revocation would make them ineligible for various benefits available to registered organizations.

The sending of leaflets across the border by activist groups has emerged as a major source of cross-border tensions since Pyongyang called it a violation of an inter-Korean summit agreement and threatened to take a series of retaliatory steps against South Korea if it did not stop such activity.

North Korea also called South Korea an "enemy" and blew up a joint liaison office in its border town of Kaesong in anger over the leafleting issue last month.