UN Secretary-General António Guterres has expressed concern over North Korea's failure to respond to regular contact with South Korea for several days.

According to Voice of America, deputy spokesman for the UN chief Farhan Haq said on Tuesday that the secretary-general remains concerned about the rising tensions on the Korean Peninsula and has consistently called for the resumption of talks to foster an environment conducive to dialogue.

The official said the reopening and strengthening of communication channels, particularly the inter-Korean liaison and military communication channels, are needed to lower the risk of miscalculation and reduce tensions in the region.

Seoul's unification and defense ministries said on Wednesday that the North has remained unresponsive to liaison office and military hotline calls for the sixth day.

On Tuesday, unification minister Kwon Young-se issued a statement voicing strong regret over what he called Pyongyang's unilateral and irresponsible attitude.

The two Koreas hold regular phone calls twice a day, in the morning and afternoon, via the joint liaison office as well as their military channel.