South Korea announced Sunday that it would resume loudspeaker propaganda campaigns against the North, after Pyongyang sent a fresh barrage of trash-filled balloons across the border.

"We will install loudspeakers against North Korea today and carry out the broadcast," the president's office said in a statement.

It added that "the responsibility for the escalation of tension between the two Koreas will be entirely up to the North."

North Korea sent more than 300 trash-filled balloons across the border in a fresh blitz starting Saturday, Seoul's military said, with the president's office saying this had forced it to take "corresponding measures".

"Although the measures we are taking may be difficult for the North Korean regime to endure, they will deliver messages of light and hope to the North Korean military and citizens," it added.

In recent weeks, activists in the South have floated dozens of balloons bearing K-pop, dollar bills and anti-Kim Jong Un propaganda northwards, infuriating Pyongyang which has retaliated in kind.

Pyongyang sent nearly a thousand balloons carrying cigarette butts and toilet paper across the border late May and early June, before calling off its campaign.

It restarted Saturday in response to new launches last week by the activists, which Seoul's government is almost entirely legally powerless to prevent.

The Seoul city government, as well as officials in surrounding Gyeonggi province, sent out a text alert to residents on Saturday, warning about the new balloons.

"North Korea is making another low-class provocation with trash balloons against our civilian areas," wrote Seoul mayor Oh Se-hoon in a Facebook post.

Seoul's military said an "analysis shows there were no substances that were harmful to safety," with the latest batch of balloons containing waste paper and plastic -- but it warned the public to stay away and report any balloons to authorities.

- Low point in ties -

Seoul's move to resume the loudspeaker broadcasts could have serious implications, experts said.

Past propaganda tit-for-tats have had real-world consequences for inter-Korean relations.

The loudspeaker broadcasts, a tactic which dates back to the 1950-1953 Korean War, infuriate Pyongyang, which has previously threatened artillery strikes against the loudspeaker units unless they were switched off.

"There is a high possibility the resuming of speakers could lead to an armed conflict," Cheong Seong-chang, director of the Korean peninsula strategy at Sejong Institute, told AFP.

"With the resuming of the speakers, North Korea will not stay put. It is likely that North Korea will resume firing in the West Sea or fire at the balloons if the South sends any again," Cheong said.

"North Korea has been jamming GPS signals for several days last week and it is likely for this kind of provocation to appear in a much stronger form in the West Sea as well."

Ties between the two Koreas are at one of their lowest points in years, with diplomacy long stalled and Kim ramping up his weapons testing and development, while the South draws closer to major security ally Washington.

In 2018, during a period of improved inter-Korean relations, the leaders of the two Koreas agreed to "completely cease all hostile acts against each other in every domain", including the distribution of leaflets.

The South Korean parliament passed a law in 2020 criminalising the act of sending leaflets to the North, but the activists did not stop.

That same year, Pyongyang, blaming the anti-North leaflets, unilaterally cut off all official military and political communication links with the South and blew up an inter-Korean liaison office on its side of the border.

Last year, South Korea's Constitutional Court struck down the 2020 law, calling it an undue limitation on free speech.