South Korea will begin loudspeaker broadcasts directed at North Korea on Sunday that will be “unbearable” for the Kim Jong Un regime, its National Security Council said, after Pyongyang resumed sending balloons carrying trash across the border.

The council met on Sunday morning, after dozens of balloons with trash attached were found in Seoul and in areas near the border earlier in the day and overnight.

“The measures we will take may be unbearable for the North Korean regime but they will send a message of hope and light to the North’s troops and its people,” the council said.

South Korea has warned it would take “unendurable” measures against the North for sending the trash balloons, which could include blaring propaganda broadcasts from huge loudspeakers set up at the border directed at the North.

Pyongyang started sending balloons carrying trash and manure across the border in May and has said the move was in retaliation to anti-North leaflets flown by South Korean activists as part of a propaganda campaign.

On June 2, it said it would temporarily halt sending the balloons because 15 tonnes of trash it sent was probably enough to get the message across on how “unpleasant” it was. However, it vowed to resume if leaflets were again flown from the South by sending hundred times the amount.

A group of South Korean activists defied the warning and have since flown more balloons to the North with leaflets criticising its leader Kim Jong Un together with USB sticks containing K-pop videos and dramas, and US dollar notes.

North Korea has shown some of the angriest reactions towards the leaflet campaign and the loudspeaker broadcasts, in some cases firing weapons at the balloons and speakers in the past.

South Korea stopped the broadcasts under an agreement signed by the two Korea’s leaders in 2018 declaring a new era of peace and harmony and vowing to ease military tensions to eliminate the chances of another war breaking out.

But tensions have mounted since then as North Korea pushed ahead with the development of ballistic missiles and declared it sees South Korea as its “enemy number one”, unveiling a range of weapons that it said were aimed at the South.

South Korea’s broadcasts are blasted from multiple speakers stacked in large racks and include world news and information about democratic and capitalist society with a mix of popular K-pop music. The sound is believed to travel more than 20km (12.4 miles) into North Korea.

South Korea’s military said the North launched about 330 balloons with trash attached starting Saturday and about 80 of them dropped in South Korea.