North Korean leader Kim Jong-un has consolidated his power in a short period of time since he took office in late 2011, but the North's isolation has seriously deepened due to his obsession with nuclear weapons, analysts said.

The North's young leader Kim inherited power four years ago when his father Kim Jong-il died of heart failure.

In his late 20s, Kim became the North's leader just three years after he was anointed the heir-apparent, necessitating his drive to consolidate power in a short period of time.

"Kim chose the reign of terror for a governing style," said Yang Moo-jin, a professor at the University of North Korean Studies. "He has brutally dealt with disobedient officials while displaying the image of a caring leader for ordinary North Koreans."

Since assuming power, Kim has executed around 100 party and military officials, according to the Institute for National Security Strategy.

He ordered the execution of his once-powerful uncle Jang Song-thaek for treason two years ago. Former defense chief Hyon Yong-chol was killed with an anti-aircraft gun over his alleged disloyalty to Kim.

The iron-fisted rule has helped the North's leader reshuffle old-time officials and set up his own legacy, but a growing number of officials are also disenchanted with his rule, seeking asylum in South Korea and other countries, experts said.

"What strikes in the North's power structure is an emergence of new power elites in their 40s and 50s," said Kim Yong-hyun, a professor of North Korean studies at Dongguk University. "A shift in generations will continue among party officials."

Analysts said that the planned congress of the ruling Worker's Party of Korea will be a watershed for gauging the direction of Kim's governing rule.

The WPK plans to hold the congress for the first time in more than three decades in May where Kim is likely to conduct reshuffle and unveil a new line of state policies.

Yang said Kim may loosen the severity of the reign of terror ahead of the key party event, but his pursuit of purges will continue as it is a common governing style in dictatorial socialist countries.

Touching on external affairs, North Korea has seen its isolation deepen under Kim's regime due to the country's persistent pursuit of nuclear weapons program. The North has conducted nuke tests in 2006, 2009 and 2013.

Kim is seeking a dual pursuit of developing nuclear arsenals and boosting its fragile economy, commonly known as the "byeongjin" policy. Seoul and Washington have warned that the North's dual-track policy a dead end for it.

Also he has not held any summit with leaders from other countries including China, the North's traditional ally.

Relations between North Korea and China have been sharply strained since the North's 2013 nuke test though some signs of improvement have emerged since October when a ranking Chinese official visited the North for a military parade.

Meanwhile, South and North Korea reached a rare deal in August on defusing military tension following heightened tension sparked by a landmine blast near the inter-Korean border blamed on North Korea.

The two sides are scheduled to hold a vice-ministerial meeting on Friday to discuss pending issues, but there is a big gap between the two over main agenda items for the talks.

Seoul puts a priority on regularize reunions of families separated by the 1950-53 Korean War while Pyongyang calls for the early resumption of a suspended joint tour program at Mount Kumgang in the North.

"Whether to resume the tour program is not a simple issue as it is linked to the North's nuclear problem as U.N. Security Council sanctions on the North bans transfer of bulk cash to Pyongyang," said Chang Yong-seok, a researcher at the Seoul National University Institute for Peace and Unification Studies.

He also said that the North is facing very serious isolation as it is under relevant U.N. sanctions banning the North's nuke and missile tests.

"North Korea is expected to focus on handling external relations for the time being ahead of the party congress," he said. (Yonhap)