North Korea is again flying balloons likely carrying rubbish toward South Korea, days after South Korea’s military boosted anti-Pyongyang propaganda broadcasts across the rivals’ heavily armed border.

South Korea’s Joint Chiefs of Staff said in a statement on Wednesday the North Korean balloons are flying north of Seoul after crossing the border. It urged the South Korean people to be alert for falling objects.

Wednesday’s balloon activities by North Korea were the tenth of their kind since late May. North Korea has argued its balloon campaigns were a response to South Korean activists scattering political leaflets across the border via their own balloons.

South Korea on Sunday said it was bolstering its anti-Pyongyang propaganda broadcasts from its loudspeakers along the land border because North Korea was continuing launches of rubbish-carrying balloons.

The tit-for-tat Cold War-style campaigns between the two Koreas are inflaming tensions on the Korean Peninsula, which remains in a technical state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty.