SEOUL, South Korea (AP) — The South Korean military said North Korea disrupted GPS signals from border areas for the second day in a row on Saturday, affecting an unspecified number of flights and ship operations.

Tensions between the rival Koreas have escalated under North Korea’s leadership Kim Jong-un shows off his advancing nuclear and missile program and engages in electronic and psychological warfare, such as flying thousands of balloons drop trash and anti-South Korean propaganda leaflets in the South.

South Korea’s Joint Chiefs of Staff said North Korean operations to manipulate GPS signals were detected Friday and Saturday around the western border city of Kaesong and the nearby city of Haeju, and said the activities disrupted dozens of civilian aircraft and several ships.

While the South Korean military alerted planes and ships near the western border areas, it did not specify how North Korea disrupted GPS signals or provide details on the extent of the disruptions.

“We urge North Korea to immediately stop GPS interference provocations and strongly warn that the country will be held fully responsible for any resulting consequences,” the South’s joint leaders said in a statement.

North Korea’s GPS signal jamming and balloon campaigns highlight the vulnerability of South Korea’s Incheon International Airport, its main transportation gateway, analyst Sukjoon Yoon recently wrote on the North Korea-focused 38 North website.

The airport, which transports 56 million people and 3.6 million tons of cargo annually, is less than 100 kilometers from North Korea.

“There have been no major aviation incidents to date, but GPS interference can endanger commercial airlines flying in poor visibility, and it violates international conventions on navigational safety,” Yoon wrote. He said North Korean garbage balloons shut down the airport’s runway operations 12 different times in 2024, for a total of 265 minutes.

Kim has shown more hostility this year towards Seoul’s conservative government – which maintains a hard line on Pyongyang – with the North abandoning its long-standing goals of reconciliation with its war-divided rival. rewriting its constitution to strengthen South Korea as a permanent opponent.

North Korea too has blown up parts of its unused road and rail lines allied with the South in October in a symbolic expression of anger toward Seoul, and opened November with a flight test of a new intercontinental ballistic missile to increase pressure on Washington.

South Korean officials say North Korean activities to disrupt GPS signals from western border areas increased as the country began launching waste-bearing balloons towards the South at the end of May, which the North described as a retaliation against South Korean civil activists flying anti-North Korean propaganda leaflets across the border.

Beyond North Korea’s weapons demonstrations and non-conventional provocations, there is growing concern over the reported supply of military equipment and troops to Russia in support of President Vladimir Putin’s war against Ukraine. South Korean officials say deepening military cooperation between Moscow and Pyongyang could potentially result in Russian technology transfers that increase the threat of Kim’s military nuclear program.