North Korea has intensified efforts to idolize its leader Kim Jong-un ahead of the upcoming party congress, but its excessive drive may be causing ill feelings among its people, a Seoul official said Thursday.

North Korea has strengthened the personality cult of the current leader since Kim took office in late 2011 following the sudden death of his father Kim Jong-il.

"On the occasion of the party congress, the North is expected to boost the level of the idolization of Kim Jong-un to near that of his late grandfather Kim Il-sung and Kim Jong-il," said an official at Seoul's unification ministry.

The Workers' Party of Korea plans to hold its first party congress in more than 30 years next Friday, a move expected to help the leader reaffirm his tight grip on power.

The ministry said North Korea has reinforced its move to idolize Kim following the execution of Jang Song-thaek, the once-powerful uncle of the incumbent leader, in December 2013, in a bid to highlight the one-man leadership system.

Pyongyang has also further exalted Kim by focusing on his capabilities and accomplishments since the North's nuclear test in January and long-range rocket launch in February.

North Korea has threatened to carry out another nuclear test or fire off a mid- or long-range missile in apparent defiance of tougher U.N. sanctions imposed on the North in March.

The government said the upcoming party congress will be a good occasion for the North to boost the personality cult of Kim and elicit allegiance to the leader.

But the North's idolization campaign may hit a snag over the long term as it will not actually bring about any improvements to the livelihood of ordinary North Koreans, the ministry said.

North Korea has mobilized ordinary citizens to prepare for the congress under the "70-day campaign of loyalty" and forced them to offer money to authorities, inviting growing discontent from its people according to the government official.

"The North's idolization drive could rouse ill feelings among ordinary people and youths, possibly providing a source of instability for the regime," it said. (Yonhap)