Pyongyang: North Korea's power brokers on Thursday declared Kim Jong Un the supreme leader at a massive public memorial for his father Kim Jong Il, cementing the Kim family's hold on power for another generation.

The son, dubbed North Korea's Great Successor, stood with his head bowed and somber in a dark overcoat on a balcony at the Grand People's Study House overlooking Kim Il Sung Square and watched the memorial that doubled as a show of support for his burgeoning role as leader.

The unequivocal public backing for Kim Jong Un at his father's memorial provides a strong signal that government and military officials have unified around him in the wake of Kim Jong Il's death on December 17.

As he stood overlooking a sea of humanity gathered below him in Pyongyang's main square, Kim Jong Un was flanked by top party and military officials, including Kim Jong Il's younger sister, Kim Kyong Hui, and her husband Jang Song Thaek, who are expected to serve as mentors of their young nephew.

Given Kim Jong Un's inexperience and age -- he is in his late 20s -- there are questions outside North Korea about whether he is equipped to lead a nation engaged in long- stalled negotiations over its nuclear programme and grappling with decades of economic hardship and chronic food shortages.

But support among North Korea's power brokers was clear at the memorial service, which was attended by hundreds of thousands of people filling Kim Il Sung Square and other plazas in central Pyongyang.

"The fact that he completely resolved the succession matter is Great Comrade Kim Jong Il's most noble achievement," Kim Yong Nam, president of the Presidium of the Supreme People's Assembly, told the massive audience at the square.

"Respected Comrade Kim Jong Un is our party, military and country's supreme leader who inherits great comrade Kim Jong Il's ideology, leadership, character, virtues, grit and courage," said Kim, considered North Korea's ceremonial head of state.

(Agencies)