Seoul’s Defense Ministry said Wednesday the flying vehicles that prompted warning shots after crossing the border a day ago were found to be “balloon-shaped” gadgets apparently carrying propaganda leaflets against South Korea.

Several objects were detected breaching the Military Demarcation Line near Cheorwon Country, Gangwon Province, between 5 p.m. and 8:30 p.m. Tuesday, inducing the South Korean Army to broadcast warnings and then fire hundreds of rounds of K-3 machine gun, according to the Joint Chiefs of Staff.

“Based on various monitoring equipment we assess that they were North Korean instruments designed to spray anti-South leaflets,” ministry spokesperson Moon Sang-kyun said at a news briefing.

“The objects appeared to assume the form of balloons, and most of them were moving from west to east according to the direction of the wind before they disappeared.”

Shortly after the incident, speculation aroused the objects may possibly be unnamed aerial vehicles flying in from the North, which have in the past fueled criticism over Seoul’s lax air defense. The military said it had trouble making its initial assessment due to bad weather conditions.

The JCS also dismissed the possibility that the balloons were launched by South Korean civic groups, citing its radar imagery that showed different looks -- North Koreans typically use round bags, unlike the South‘s rod-shaped ones.

On Monday night, a group of South Korean activists flew 10 balloons carrying about 300,000 anti-Pyongyang flyers, 2,000 US dollar bills and 500 booklets from Paju, Gyeonggi Province.

”In addition to the balloons’ sphere form and irregular movment, we witnessed their explosion, as well as the fallen leaflets afterward,” a JCS official told reporters on condition of anonymity, noting the devices were apparently designed as self-destructive.

North Korea has long been sending propaganda leaflets toward the South, even after the inauguration of President Moon Jae-in, who signaled a shift in Seoul‘s approach toward dialogue with Pyongyang.

On May 14, South Korean police said they found about 10,000 brochures in northern Seoul which carried messages calling for “building a strong nuclear state” and “fighting against the US.”

“Regardless of the government change, North Korea will continue to do what it has done before. If a similar situation occurred, we would postulate the worst-case scenario and respond as we did before by treating such objects as UAVs,” the JCS official added.

By Yeo Jun-suk (jasonyeo@heraldcorp.com)