Inter-Korean communication channels remain suspended for the fourth straight day, following Pyongyang's strong protest over Seoul and Washington's annual combined military exercises.

The Unification Ministry said on Friday that Seoul could not get in touch with Pyongyang for their daily morning call at 9:00 a.m. through the liaison channel.

The Defense Ministry also failed to reach the North through its two military hotlines.

Since restoring cross-border direct communication after 13 months on July 27, the two Koreas have been connecting twice daily.