SEOUL (AFP, REUTERS) - A delegation of North Korean officials and ice hockey players crossed the heavily guarded border into South Korea on Thursday (Jan 25)for joint Olympics training, as Pyongyang called for all Koreans to seek unification of the two nations.

The group included 12 North Korean players who will form a combined women's ice hockey team with their southern counterparts at next month's Winter Olympics in the South Korean mountain resort of Pyeongchang.

Stepping off a bus after driving through large gates on the border, the athletes ignored questions as they were mobbed by throngs of media. They wore puffy winter jackets in the white, blue, and red colours of North Korea's flag, with "DPR Korea" emblazoned on the back, referring to the country's official name, the Democratic People's Republic of Korea.

After going through South Korean checkpoints at the border, the team traveled to a national training centre in Jincheon, 90 km south of Seoul.The skaters, wearing North Korean team tracksuits, crossed the land border by road near Kaesong, Seoul's unification ministry said.

They accompanied a sports delegation from Pyongyang who will prepare for the arrival of its other athletes for next month's Games in Pyeongchang, east of Seoul.

Under an agreement worked out during the first official talks between the two Koreas in two years, the joint team will wear unity jerseys and march under a unified peninsula flag at the Games' opening ceremony on Feb 9.

Earlier on Thursday, North Korea sent a rare announcement addressed to "all Koreans at home and abroad", saying they should make a "breakthrough" for unification without the help of other countries, its state media said.

All Koreans should "promote contact, travel, cooperation between North and South Korea" while adding Pyongyang will "smash" all challenges against reunification of the Korean peninsula.

The announcement, issued after a joint meeting of government and political parties, added Koreans should try to ease military tensions and create a peaceful climate on the Korean peninsula.

North and South Korea remain technically at war after their 1950-53 conflict ended in a truce rather than a peace treaty.

Tensions escalated dramatically last year as the regime of Kim Jong Un stepped up its programme aimed at developing a missile capable of striking the United States with a nuclear warhead.

The Pyeongchang Winter Olympics have triggered an apparent rapprochement on the divided peninsula.

US Vice President Mike Pence plans to use his attendance at the Winter Olympics in South Korea next month to try to counter what he sees as North Korean leader Kim Jong Un's efforts to "hijack" the games with a propaganda campaign, a White House official said on Tuesday.

Washington has been driving a tightening of sanctions on isolated North Korea and on Wednesday (Jan 24), imposed fresh sanctions on nine entities, 16 people and six North Korean ships it accused of helping the weapons programmes.

It also urged China and Russia, North Korea's main allies, to expel North Koreans raising funds for the programmes.

The South Korean government has rejected criticism that the games had been hijacked by North Korea, saying the event will help defuse tensions over Pyongyang's nuclear and missile programme.

But the unified women's ice hockey team has provoked controversy in the South, with accusations that Seoul is depriving some of its own players of the chance to compete at the Olympics for political purposes.

Concerns have also been expressed that the sudden addition of so many players so close to the competition - for which South Korea qualified as hosts, rather than on merit - will disrupt team chemistry.

Public anger in the South has also been fanned by senior Seoul officials who sought to justify the decision on the grounds that the female team had no real medal chances anyway.

The row has taken a toll on the popularity of dovish South Korean President Moon Jae In, whose latest job approval ratings dived to 60 per cent - the lowest since he took office last May.

The RealMeter survey blamed the controversy over the joint team and public perception that Moon's administration made too many concessions to the North to secure its participation at the Olympics.

Pyongyang will have another 10 athletes taking part in the Games: three cross-country skiers, three alpine skiers, two short-track speed skaters and two pairs figure skaters.

The figure skaters, Ryom Tae Ok and Kim Ju Sik, are the only North Korean athletes to have met the Winter Olympics qualifying standards.