North Korea appears to be installing loudspeakers on the front lines on Thursday, a day after South Korea resumed the anti-Pyongyang broadcasts from near the border for the first time in six years, according to South Korea’s Joint Chiefs of Staff.

The JCS said in a message to reporters Monday that North Korea was believed to be preparing for their own broadcasts targeting the South across the border.

“We have identified signs of North Korea setting up loudspeakers in the border areas. So far no broadcast has played out from the loudspeakers yet, and we are closely monitoring further developments and military readiness,” the JCS said.

The JCS added that South Korea was “ready to restart our broadcast as soon as North Korea does something despicable.”

From around 5 p.m. Sunday, the South Korean military-produced broadcast was played for around two hours with the loudspeakers into the North.

Col. Lee Sung-jun, the JCS spokesperson told reporters the broadcast was being operated “from protected areas that are prepared to respond immediately in case of a possible military action from North Korea.”

After taking a break for six days, North Korea once again sent balloons carrying trash into South Korea each day of the weekend.

The release of the balloons, timed to coincide with a southward wind, came after a South Korean activist group called Fighters for Free North Korea tried to float about a dozen K-pop propaganda balloons on Thursday. The JCS said a few of them crossed the border to the North.

The group said the balloons carried anti-Kim Jong-un regime leaflets and removable USB drives containing South Korean pop culture content like K-pop and K-dramas -- which North Korea had earlier warned they would retaliate against.

Announcing a pause in releasing balloons on June 2, Kim Kang-il, the North Korean vice defense minister, said any propaganda leaflets coming from the South would be met with “spraying of a hundred times the amount of the filth that had been sent.”

According to the JCS’ latest count as of Monday morning, the number of North Korean balloons launched in two waves on Saturday and Sunday respectively stands at around 300.

The JCS said that the 300-something balloons collected from the latest round appeared to contain wastepaper, pieces of plastic and other garbage. Unlike the first two times, nothing believed to be excrement was found in the balloons based on the initial assessment, the JCS added.

Some of the balloons never made their way to South Korea and landed in the North, after the wind changed its course, according to the JCS.

Shin Beom-chul, Seoul’s former defense vice chief, says North Korea restarting the balloon launches is likely its reaction to the South Korean activist group flying anti-Kim leaflets.

“North Korea said they will retaliate with more balloons if such leaflets were to be sent from South Korea. I think we can take their words at face value in this instance,” he told The Korea Herald.

Shin did not think however that there was a way the South Korean government could stop individual groups from flying leaflets and other things that North Korea deems as propaganda.

Apart from the Constitutional Court declaring the ban on anti-North Korea leaflets to be unconstitutional in September last year, South Korea “could give North Korea the wrong signal” by restricting the activism, he said.

“Our government stepping up and sending a message anti-North Korea leaflets at this stage would be like rewarding Pyongyang for their behaviors. We might reinforce what they are doing with balloons and other provocations by doing so,” he said.

The trash balloons have turned out to be an effective way of “bugging South Korea, without costing them too much while at the same time causing a scene,” according to Park Won-gon, professor of North Korean studies at Ewha Womans University in Seoul.

He pointed out that despite a clear warning from the South Korean government with the resumption of loudspeaker broadcasts along the border on Sunday, North Korea took a risk by flying the balloons again.

“The border broadcasts are quite painful for Kim Jong-un, as it is mostly North Korea’s Gen Zers and millennials who are on the front lines. The younger generations, already in touch with the outside world and disillusioned with the regime, will be the ones listening to the broadcasts of South Korean news,” he said.