The foreign ministry is attempting to locate a South Korean marine who departed for Poland without permission in order to enter Ukraine.

The ministry said it confirmed that the marine left a Polish Border Guard building in the early hours on Wednesday. However, a ministry official said the soldier’s whereabouts are unknown as he has failed to respond to the ministry’s calls.

The marine had holed up in the building after his attempt to enter Ukraine from Poland failed.

The ministry said it will work closely with Polish and Ukrainian officials to track down the marine so that he can return home safely.

According to the military, the marine left for Warsaw from Incheon International Airport on Monday while on leave. His action is considered to be a desertion of military service as active-duty service members must secure permission if they want to go abroad while on leave.

One media outlet reported that the marine said in a telephone conversation that he was leaving the country to join international volunteer fighters assisting Ukraine in the war with Russia.