State television in North Korea has for the first time showed live pictures of leader Kim Jong-il with his son and presumed heir, Kim Jong-un.
Kim Jong-il's youngest son accompanied him to a huge military parade in the capital to mark the 65th anniversary of the ruling Workers' Party.
Kim Jong-un is thought to be in line to succeed his father as leader of the highly secretive state.
He was suddenly promoted to senior leadership roles last month.
Kim Jong-un, dressed in a dark blue civilian suit, sat next to his father on a viewing platform at Kim Il-sung Plaza as tanks with rocket-propelled grenades and long-range missiles rolled by.
The missiles carried the slogan of the Korean People's Army: "Defeat the US military. US soldiers are the Korean People's Army's enemy."
Thousands of troops goose-stepped around the plaza, which was decorated with banners and flags.
Ordinary citizens were waving plastic bouquets.
Officials say the anniversary celebrations will be biggest of their kind in the nation's history.
On Saturday, father and son had appeared at a festival in the capital.
Members of the international media were also invited in to witness the event.
As a spotlight shone on the two men, the massive crowd at the Arirang gymnastics and dance festival rose to their feet and burst into applause.
Last month, the Swiss-educated Kim Jong-un was made a four-star general and given senior positions in the government and the Workers' Party, at a rare party conference.
Analysts say this means he is in line to succeed his father, who took over the leadership of North Korea in 1994 after his father, Kim Il-sung, died. However, the title of President has been assigned "eternally" to Kim Il-sung.
Little is known about Kim Jong-un, who is believed to be about 27 years old,.
He would take the Kim dynasty rule over the nation of 24 million into the third generation.
"The future of our country is rosy and bright because Kim Jong-un was elected vice chairman of the military commission of the Workers' Party," said a government official.
"We have a proverb in Korean that great teachers produce great students and great parents produce great children," the official added.
Kim Jong-il is thought to be in poor health and is widely believed to have suffered a stroke two years ago.
The 68-year-old, dressed in his customary khaki tunic suit, stood for over an hour during the parade and waved to the crowds, but he limped noticeably and reached to the balcony for support.
North Korea is locked in a dispute with the West over its nuclear weapons programme and is struggling to revive its crumbling economy.