North Korea sends hundreds more trash-filled balloons south

North Korea has sent more trash-filled balloons southward, Seoul's military said Tuesday, the latest in a series of border barrages that have sparked a tit-for-tat propaganda campaign.

Pyongyang launched about 350 balloons on Monday evening and then launched more late on Tuesday, Seoul's Joint Chiefs of Staff (JCS) said.

Around 100 of those launched on Monday had landed in the South, mainly in northern Gyeonggi province and the capital Seoul, the JCS said.

The bags attached to those balloons contained "mostly paper waste", the military said, adding that they posed no safety risk to the public, according to their analysis.

"The South Korean military is ready to carry out its psychological warfare immediately," the JCS said, adding the response "all depends on North Korea's actions".

South Korean President Yoon Suk Yeol said in a speech marking the anniversary of the start of the Korean War that the North's latest round of trash-carrying balloons was a "despicable and irrational provocation".

He slammed a deal between Pyongyang and Moscow, signed last week by Russian President Vladimir Putin during a state visit to North Korea, as a "blatant violation of UN Security Council resolutions".

"Our military will maintain a steadfast readiness to ensure that North Korea does not dare to challenge South Korea under any circumstances and will respond overwhelmingly and decisively to any provocations from the North," Yoon said.

Pyongyang has already sent more than a thousand balloons carrying trash southward in what it says is retaliation for balloons carrying propaganda criticising Kim Jong Un's rule floated north by activists.

In response, Seoul has fully suspended a tension-reducing military deal and restarted some propaganda broadcasts from loudspeakers along the border.

Kim Jong Un's sister and key government spokeswoman Kim Yo Jong warned this month that Seoul would "undoubtedly witness the new counteraction of the DPRK" if the leaflet drops and loudspeaker broadcasts continued.

Experts said border tensions could potentially escalate quickly.

"Since the South has met the first condition -- which is the leaflet scattering -- if the government were to resume loudspeakers, we would likely see the 'new counteraction' that was mentioned," said Park Won-gon, a professor at Ewha Women's University.

On Tuesday, Yoon visited a U.S. aircraft carrier that arrived in South Korea at the weekend for joint military drills aimed at better countering North Korean threats.

The drills, which include Japan, are set to go ahead later this month.

Pyongyang has routinely criticised such drills as rehearsals for an invasion.