South Korea's top court ruled that it is legitimate for the government to curb activists from sending anti-Pyongyang leaflets across the border, citing security issues, official records showed Monday. 

The Supreme Court in late February turned down a suit filed by Lee Min-bok, 59, seeking compensation from authorities for causing what he called "mental distress" by preventing his leaflet launch.

The court said the leaflet campaign can be restricted if it threatens the safety of ordinary people, despite the North Korean defector's claim that it is an expression of his freedom of speech. 

The leaflet campaign is a source of tension between the two Koreas. 

Lee, a high-profile leaflet activist, and his supporters have been sending the leaflets from 2005 onwards, after he defected from the North in 1991.

The South Korean government has been restricting Lee's campaign since 2007, when he tried to send them from populated residential or commercial areas, citing possible provocations from the North.

Pyongyang has on numerous occasions threatened to attack leaflet launch sites.

In October 2014, South and North Korea exchanged fire across the tense border after the North used anti-aircraft machine gun rounds to shoot down balloons carrying anti-Pyongyang propaganda launched by Lee.  (Yonhap)