An activist group's attempt to send anti-North Korea propaganda leaflets across the border likely failed on Monday night, Seoul's unification ministry said Tuesday, raising possible concerns that the group lied about the size of its cross-border launch.

"The head of Fighters for a Free North Korea (FFNK), Park Sang-hak, on Monday night claimed that [the group] scattered 500,000 leaflets using 20 large-size balloons in the city of Paju. However, circumstances show that [this information] is unreliable," South Korea's Ministry of Unification (MOU) said in a statement on Tuesday evening.