North Korea's decision to not welcome foreign delegations to the funeral of former leader Kim Jong-il has some analysts in South Korea speculating about instability in the North, with the abrupt death of Kim heightening the uncertainty surrounding his untested heir-apparent.

North Korea declared a 13-day mourning period through Dec. 29 from the day of Kim's death on Saturday, while stating it will not accept foreign delegations at a state funeral set for Dec. 28 in Pyongyang. No entertainment will be allowed during the mourning period.

The decision against inviting foreign delegations to the funeral of Kim, who died of a heart attack, is a parallel to the funeral of his father, the North's founder Kim Il-sung. Some analysts, however, said Pyongyang may have no choice but to shun foreign delegations to hide its internal weakness.

"The reason North Korea won't accept foreign delegations appears to be that the North's leadership may have not sorted out its internal stance," said Cha Doo-hyeon, a senior analyst at the state-run Korea Institute for Defense Analyses.

Since the death of Kim was announced on Monday, North Korea has urged its people to rally behind the heir-apparent Kim Jong-un, who is believed to be in his late 20s.

The leader-in-waiting was made a four-star general and given top ruling party posts last year, but has yet to take over the posts held by his father, including as chairman of the omnipotent National Defense Commission.

"Under North Korea's constitution, there are no clauses on the death of the chairman of the National Defense Commission and who will assume the acting chairman role," Cha said.

While Kim Jong-il had prepared for 14 years to take the reins of North Korea from his father, who died in 1994, his youngest son only made his public debut just last year.

In a sign that the younger Kim is in charge, however, his name topped a list of 232 party and military officials on a national funeral committee.

Japan, China, Russia and other nations have expressed "condolences" on the death of Kim, but South Korea has yet to decide whether to offer condolences, because of concern such a gesture could bring a backlash from conservatives ahead of next year's general elections.

John Delury, a professor at Seoul's Yonsei University Graduate School of International Studies, urged South Korea and the United States to expand their engagement with North Korea.

"North Korea is now making only the second political transition of its 60-plus-year history," Delury wrote in a commentary.

"And thus far, there is no evidence of near-term political crisis or confusion as to the new pecking order; no sign of factional struggles, popular revolt, or systemic breakdown," the professor said.

The most important role for key players on the Korean Peninsula

-- South Korea, the U.S. and China -- is to expand channels with North Korea.

"The more we know about the new leadership, the better we can respond," Delury said. "The downside of engagement is minimal, but the costs and risks of isolating North Korea at this point are steep." (Yonhap News)