Dozens of elderly and frail South Koreans entered the North Monday to meet relatives for the first time since the peninsula and their families were divided by war nearly seven decades ago.

The three-day reunion -- the first for three years -- will take place at Mount Kumgang, a scenic resort in North Korea, following a rapid diplomatic thaw between the neighbours.

North Korean state media blamed Donald Trump's political opponents for the "deadlock" over denuclearisation on Saturday, urging the US President to act boldly to make progress on the thorny issue.

Trump and the North's leader Kim Jong Un held a groundbreaking summit in Singapore in June, which the US leader touted as a historic breakthrough.

North Korea said it had fully demolished its only known nuclear test site on Thursday, with a series of planned detonations that put the facility beyond further use.

U.S. President Donald Trump hailed Friday's Korea summit as historic but warned that "only time will tell."

The North Korean train that arrived in Beijing this week looked remarkably similar to one used by the North's late leader Kim Jong Il, its olive-green exterior and yellow stripe prompting intense speculation his son and successor Kim Jong Un was on board.

Six years after inheriting power from his father, Kim Jong Un has established his authority domestically, taken North Korea to unprecedented nuclear heights, and is now looking to flex his muscles abroad.

South Korean President Moon Jae-in and the North's ceremonial head of state Kim Yong Nam met and shook hands Friday ahead of the Winter Olympics opening ceremony.

Dramatic footage of a North Korean soldier's defection released Wednesday showed him racing across the border under fire from former comrades, and then being hauled to safety by South Korean troops.

The footage also showed a North Korean guard briefly crossing the border in hot pursuit before retreating --  an incident the US-led United Nations Command described as a serious breach of the 1953 ceasefire that ended Korean War hostilities.

The European Union blacklisted the North Korean army on Monday as part of fresh sanctions aimed at punishing the pariah regime for its nuclear and ballistic weapons programs.

North Korea Tuesday condemned "vicious" new U.N. sanctions imposed over its sixth and largest nuclear test, warning it would make the U.S. "suffer the greatest pain" it has ever experienced.

The new sanctions imposed unanimously by the U.N. Security Council Monday ban North Korean textile exports and restrict shipments of oil products.