This file photo taken Aug. 22 shows the Imjin River flowing through Yeoncheon, a border county about 50 kilometers north of Seoul. (Yonhap)

North Korea appears to have discharged a "considerable" amount of water from the upstream of its dam near the inter-Korean border, Seoul's environment ministry said Wednesday.

Satellite imagery taken at 3 p.m. showed the downstream of the Imjin River had significantly broadened in width, according to the ministry.

The water level of South Korea's northernmost Pilseung Bridge on the Imjin River had reached 1 meter as of 5 p.m., up from 0.3 meter recorded three hours before.

The Ministry of Environment has notified related authorities, including the military and the local government, of the situation after assessing signs of possible water discharge and activating an emergency response system. (Yonhap)