SEOUL, South Korea (AP) — North Korea launched more balloons likely carrying rubbish toward South Korea on Sunday, two days after the South restarted blaring anti-Pyongyang propaganda broadcasts across the border in retaliation for the North’s repeated balloon campaigns, Seoul officials said.

South Korea’s Joint Chiefs of Staff said the North Korean balloons were flying north of Seoul, the South Korean capital, after crossing the border.

It said the South Korean public should be alert for falling objects and report to police and military authorities if they see any balloons fallen on the ground.

North Korea’s latest balloon flying is threatening to escalate tensions on the Korean Peninsula. South Korea earlier warned it would conduct loudspeaker broadcasts in a fuller manner and take other stronger steps if North Korea continues provocations like balloon launches.

Since late May, North Korea has floated numerous balloons on a series of launch events to drop scraps of cloth, cigarette butts, waste batteries and even manure on South Korea, though they caused no major damage in South Korea.

North Korea said the initial balloons were launched in response to South Korean activists sending political leaflets to the North via their own balloons. North Korea views South Korean civilian leafleting activities as a major threat to its leadership as the country prohibits official access to foreign news for most of its 26 million people, experts say.

In a statement Tuesday, Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, warned that South Korean “scum” must be ready to pay “a gruesome and dear price” over the leafleating activities. She said more South Korean leaflets had been found in North Korea. That raised concerns North Korea could stage physical provocations, rather than balloon launches.

In response to North Korea’s balloon campaigns, South Korea responded by suspending a 2018 tension-reduction deal with North Korea, a step required for it to restart propaganda broadcasts and conduct front-line live-fire military drills at border areas. On June 9, South Korea made propaganda broadcasts for two hours at the border.