South Korea says North Korea is preparing to resume seaborne infiltration training, as ice in the North’s ports has begun to melt.

Defense Minister Kim Kwan-jin told the National Assembly on Friday that North Korea is also demanding that South Korea stop what the North is calling “psychological warfare.”

Kim said that the North is threatening to fire artillery at locations from which South Korean groups send fliers and balloons with anti-North Korean rhetoric to the North, including at Imjingak.

Kim said that North Korea used new ways to attempt to disrupt training exercises during the South Korea-U.S. Key Resolve and Foal Eagle military drills by sending global positioning system (GPS) jamming signals.

In addition, Kim cited analysis that North Korea appears to be continuing to seek additional nuclear tests and to improve missile launching facilities.

He said that the South Korean military will continue to remain vigilant even after the Foal Eagle exercises end in late April.