SEOUL, South Korea (AP) — A South Korean activists' group said Thursday it flew large balloons carrying propaganda leaflets toward North Korea, although the North has threatened to send more balloons with manure and trash across the border in response to such campaigns.

The launches are escalating animosities, with South Korea suspending a tension-easing deal with North Korea and preparing to resume frontline military activities. North Korea had halted its flights of rubbish-carrying balloons but threatened to resume them if South Korean activists sent leaflets again.

The South Korean civilian group, led by North Korean defector Park Sang-hak, said it floated 10 balloons tied to 200,000 anti-Pyongyang leaflets, USB sticks with K-pop songs and South Korean dramas and one-dollar U.S. bills from a border town on Thursday.

Park's long-running balloon activities have caused furious protests from North Korea, which is extremely wary of any outside attempt to undermine Kim Jong Un's rule. The North's state media previously called Park "human scum without an equal in the world."

After North Korea started launching hundreds of trash-carrying balloons on South Korea last week, Kim's powerful sister, Kim Yo Jong, said the campaign was meant to carry out the North's threat to conduct a tit-for-tat action against a South Korean leafleting. Observers say North Korea was referring to Park's previous balloon activities in May.

"We sent the truth and love, medicines, one-dollar bills and songs. But a barbaric Kim Jong Un sent us filth and garbage and he hasn't made a word of apology over that," Park said in a statement. "Our group, the Fighters for Free North Korea, will keep sending our leaflets, which are the letters of truth and freedom for our beloved North Korean compatriots."

North Korea's balloon campaign was seen as an attempt to cause a divide in South Korea over its conservative government's tough policy on the North. South Korean officials say they have no legal grounds to ban private citizens from flying balloons to North Korea, after the country's constitutional court last year struck down a law criminalizing such leafleting as a violation of free speech.

In reaction to the North's balloon campaign, South Korea fully suspended a 2018 tension-easing agreement with North Korea. The suspension allows South Korea to restart live-firing exercises and anti-Pyongyang propaganda loudspeaker broadcasts at border areas, actions that are certain to enrage North Korea and prompt it to launch its own military steps.

"Recently, North Korea carried out a despicable provocation that would make any normal country ashamed of itself," South Korean President Yoon Suk Yeol said in a Memorial Day speech in Seoul on Thursday. "The government will never overlook the threat from North Korea. We will maintain an ironclad readiness posture and respond to provocations resolutely and overwhelmingly."

In an apparent show of force against North Korea on Wednesday, the United States flew a B-1B bomber over the Korean Peninsula for its first precision-guided bombing drill with South Korea in seven years. North Korea has previously responded to such flyovers of advanced U.S. aircraft with provocative missile tests.

Since 2022, North Korea has aggressively intensified its weapons tests in what analysts call an attempt to expand its nuclear arsenal and wrest greater outside concessions when diplomacy resumes with the United States.