The body of North Korean leader Kim Jong-il lies in state at the Kumsusan Memorial Palace in Pyongyang in this still picture taken from video footage of still images aired by KRT (Korean Central TV of the North) December 20, 2011.
North Korea Tuesday put the body of late leader Kim Jong-Il on display in a glass coffin and heaped praise on his son and successor, amid world wariness at the transition in the nation.
South Korea sent condolences to the North Korean people despite frosty relations following two deadly border incidents last year.
And it said it would scrap a plan to display Christmas lights near the tense border because its neighbor is in mourning. North Korea has furiously objected to the plan as "psychological warfare".
In Pyongyang, state television showed a somber dark-clad Kim Jong-Un, youngest son and successor to his father, viewing the corpse along with other high officials.
An honor guard watched over the late Kim, dressed in his trademark khaki tunic and partially covered by a red flag, at Pyongyang's Kumsusan Memorial Palace.
The body of Kim Jong-Il's father, founding president Kim Il-Sung, is also on display elsewhere in the palace.
State media have reported scenes of mass grief since Kim's death from a heart attack on Saturday.
The North's official news agency touted the young and inexperienced son as the "pillar of our people".
"At the frontline of our revolution stands Comrade Kim Jong-Un, the great successor of the Juche (self-reliance) revolution and the outstanding leader of the party, military and people," it said.
"Comrade Kim Jong-Un is the unwavering spiritual and ideological pillar of our people."
The North has decreed 13 days of nationwide mourning for Kim Jong-Il. The regime kept the death a secret for two days until a tearful TV announcer disclosed it Monday and urged people to rally round his youngest son.
State TV aired footage of near-hysterical mourners, young and old alike, pounding the ground.
The news agency Tuesday carried fresh reports of grief, saying flags of mourning were flying from military bases, factories, commercial facilities and farms and endless queues of mourners were forming.
Jong-Un, who is in his late 20s, was catapulted into the limelight after his father suffered a stroke in August 2008. Last year he was made a four-star general and given top ruling party posts.
Analysts said there would be little turbulence -- at least for now -- since regime members at present have a vested interest in preserving the status quo.
"This is a turning point for North Korea whose reins have been taken by a new generation," said Cheong Seong-Chang, of Seoul's Sejong Institute think-tank.
Still, observers predict that the younger Kim will be eased into power under the tutelage of his aunt and her husband.
Obama spoke by telephone to Japan's Prime Minister Yoshihiko Noda following a conversation with South Korean President Lee Myung-Bak soon after the death announcement.
"The president underscored the United States' commitment to the defense of our close allies, including Japan," the White House said in a statement.
"He also conveyed the importance he places on maintaining the stability of the Korean peninsula and the region."
North and South Korea have remained technically at war since their three-year conflict ended only in an armistice in 1953. The United States stations 28,500 troops in the South, and another 50,000 in Japan.
Amid wariness about North Korea's future under the untested Jong-Un, Britain, France and Germany voiced hope for a new dawn after a tumultuous year that has seen regimes topple across the Arab world.
US Secretary of State Hillary Clinton said in a statement her "thoughts and prayers" were with the North Korean people "during these difficult times."
She urged the new leadership to "usher in a new era of peace, prosperity and lasting security" on the peninsula.
In Beijing, President Hu Jintao visited the North Korean embassy to offer his condolences. China, the North's sole major ally and its economic prop, has given its crucial backing to the young new leader.
"We believe that under the leadership of the Korean Workers' Party and comrade Kim Jong-Un, the DPRK (North Korean) people will unite as one and turn their sorrow into strength," said Foreign Minister Yang Jiechi.