Satellite photos have detected signs of North Korea releasing water from a dam in the border area despite South Korea's request to give prior notice, a US-based radio company reported Saturday.

The release of water from North Korea's Hwanggang Dam has raised concerns about potential flooding in areas located south of the border every summer in recent years. The dam is located in the upper region of the Imjin River, which flows through the Korean Peninsula from the north to the south.

Radio Free Asia (RFA) said satellite photos from Planet Labs, a US commercial satellite imaging company, showed some of the dam's floodgates were wide open to discharge water on July 20. They also showed visible water turbulence caused by the surging water.

The dam continued to discharge water Monday, and more floodgates were seen open Thursday, the media reported.

But the latest water discharges appear to have been made to control the water level and were not enough to cause a flood in the lower region of the Imjin River in South Korea, the radio company reported, citing a researcher at the Korea Institute for Security Strategy.

The discharges were made a few days after the South Korean government made repeated requests to Pyongyang to give prior notice if it releases water from the dam.

Under an inter-Korean agreement signed in October 2009, the North agreed to notify the South in advance of its plan to release water, following an accident that killed six South Koreans after the North discharged water from the dam without notice.

Pyongyang, however, has not implemented the agreement since 2011. (Yonhap)