South Korean police on Friday recovered over 10,000 propaganda leaflets sent by North Korea in Goyang, Gyeonggi Province, some 20 kilometers northwest of Seoul.

The leaflets are believed to be in response to the resumption of Seoul’s anti-Pyongyang broadcasts near the inter-Korean border last week, the first punitive step against the communist regime’s recent fourth nuclear test.

According to officials, 20 balloons carrying the fliers were spotted floating south from across the border between Thursday night and Friday morning. The leaflets were handed over to the military and subsequently incinerated, they said.

The balloons were attached with an automatic timer and an explosive device designed to pop them and drop the leaflets at the approximate time of arrival over Seoul or the Gyeonggi Province area, according to a government source. No GPS device was found on the balloons.

Some 30,000 leaflets have been found in the Gyeonggi area since Wednesday, police said.

The leaflets had depreciatively doctored photos of President Park Geun-hye and U.S. President Barack Obama, and featured the image of a loudspeaker with a message that can be roughly translated as “we shall disintegrate those who thoughtlessly bark at us” splattered across.

In response, Seoul said it deployed four additional movable loudspeakers with enhanced amplification capacity for its anti-North broadcasting campaign.

By Yoon Min-sik (minsikyoon@heraldcorp.com)