Seoul, South Korea (CNN) Unidentified objects which flew across the border from the North were probably propaganda balloons, South Korea's military said Wednesday.

South Korean forces fired warning shots at the unidentified objects Tuesday after they were spotted flying from North Korea across the Demilitarized Zone that divides the two countries.

"The objects were in the shape of a balloon... (and) flew in the wind's direction before disappearing," a South Korean military official told CNN. "Our military responded in accordance to our military protocol."

South Korean activists regularly send propaganda balloons into North Korea, carrying leaflets or videos. In March, a North Korean defector filled balloons with information about the murder of Kim Jong Un's half-brother, Kim Jong Nam , before floating them into the rogue state.

The suspected North Korean balloons were spotted two days after Pyongyang test-fired a ballistic missile -- its second missile test in seven days.

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