BEIJING (Yonhap) -- The chief of South Korea's state-run railway company boarded an international rail and headed for North Korea on Monday, making a rare train travel to Pyongyang from Beijing to attend an international conference concerning transport between Europe and Asia.

Choi Yeon-hye, president and CEO of the Korea Railroad Corp., and four other officials got visas from the North Korean Embassy in Beijing shortly after arriving here from South Korea earlier in the day, according to one of the KORAIL officials.

It was believed to be the first known visit by train from Beijing to Pyongyang by a high-ranking South Korean official, a diplomatic source in Beijing said.

"To my knowledge, no South Korean official publicly took the rail in Beijing to visit North Korea," the source said on the condition of anonymity.

Choi is scheduled to arrive in Pyongyang on Tuesday afternoon, according to the source.

The rare visit by Choi is aimed at attending a meeting of the Organization for Co-Operation between Railways set for April 24-28.

The rail conference in Pyongyang is meant to boost international cooperation between railway operators, bringing together top rail officials from China, Russia and 25 other member states of the OSJD.

However, attention has been focused on whether Choi and North Korean officials would discuss a plan to link South Korea's railway with Russia's trans-Siberian railway via North Korea.

Asked about whether she would discuss the plan with North Korea and Russia during the conference, Choi replied, "Nothing has been decided yet. I would know once I go there."

"And we plan to ask OSJD member states to allow South Korea to become a formal member," Choi said.

The visit comes as tensions are still high on the Korean Peninsula after North Korea fired a series of missiles and rockets off its east coast and threatened to conduct a "new form of nuclear test."

South Korea has long talked about linking its rail system with Russia's trans-Siberian railway via North Korea, though the project has made little progress due to political and security tensions in the region.

There are no direct flights between the two rival Koreas, which are still technically at war since the 1950-53 Korean War ended in a truce, not a peace treaty.