The Unification Ministry has expressed regret over North Korea's unilateral nixing of the test runs of inter-Korean railways that were slated for Thursday.

A ministry statement issued Wednesday said Pyongyang notified Seoul Wednesday morning of the cancellation due to the absence of military security guarantees for the test runs and the unstable political situation in South Korea.

Seoul blamed Pyongyang for the cancellation and said the North's reference to South Korean politics was inappropriate.

Saying the railway project should proceed without fail given its symbolic meaning for the people of the two Koreas, the ministry also urged Pyongyang to take sincere measures to conduct the test runs as soon as possible.