Inter-Korean overland travel and sea traffic are operating normally after South Korea announced Tuesday its full participation in the U.S.-led Proliferation Security Initiative (PSI).

Unification Ministry spokesman Cheon Hae-sung told a news briefing that North Korea sent a message to Seoul at around eight a.m. Wednesday permitting cross-border passage.

The spokesman said that communication between inter-Korean maritime authorities also remains normal, adding that five North Korean vessels are currently navigating on designated routes in South Korean waters in accordance with inter-Korean maritime agreements.

North Korea had previously stated that Seoul’s full membership in the PSI would be considered a declaration of war against the communist state.