North Korea is installing loudspeakers on the border with South Korea, Yonhap reported referring to South Korean military officials.

"Such moves were spotted in more than 10 regions, which have taken place simultaneously," an official of the Joint Chiefs of Staff said.

"We are closely monitoring the North's military moves," the defense ministry said. "We are fully ready to immediately respond to various possibilities."

The refusal to use propaganda on the border was one of the conditions of the military deal signed in September 2018 by the defense ministers of the two countries.