PYONGYANG (AFP) -- North Korea's new leader Kim Jong-Un on Friday led a mass rally for his late father and grandfather following the country's failed rocket launch.

The defiant launch drew condemnation from world leaders who described it as a "provocative" act that threatened regional security, despite Pyongyang insisting it was intended to put a satellite into orbit for peaceful purposes.

But Jong-Un proudly appeared for a ceremony attended by tens of thousands of people crowding a central area in Pyongyang to honour new large statues of the nation's founding president Kim Il-Sung and his son and longtime ruler Kim Jong-Il.

The ceremony, televised live, coincided with the announcement that Jong-Un was elected "first chairman" of the powerful National Defence Commission, apparently a new title.

His late father was named "eternal" chairman of the commission, the country's top decision-making body, at an annual session of the North's rubber-stamp parliament, state media said.

The new titles complete the transfer of state, military and party power from Kim Jong-Il to his son.

"Now you can say Jong-Un's new leadership is fully in place officially," Jeung Young-Tae, an analyst of Seoul's Korea Institute for National Unification, told AFP.

"He has all top party, military and state jobs under his belt. Now he's undoubtedly the top leader of the state of North Korea."

North Korea is celebrating the April 15 centenary of the birth of Kim Il-Sung with major events including the long-range rocket launch which ended in failure.

"We are holding our late great leaders in high esteem with these statues on the Mansudae hill" to mark the April 15 anniversary, Kim Yong-Nam, the North's ceremonial head of state, told cheering crowds.

Jong-Un, clad in navy Mao suit, smiled, clapped and looked up to the giant bronze statues along with top party and military cadres.

The young leader has practically assumed all top posts previously held by his father since he took over last December and was appointed as supreme commander of the country's 1.2-million army.

The new leader on Thursday assumed the new title of "first secretary" of the ruling Workers' Party of Korea, permanently leaving the top post of general secretary to his father.

The hour-long ceremony was held amid massive fireworks and hundreds of balloons released into the air while military bands played festive music.

Hundreds of participants waved flower bouquets and red paper flowers towards Jong-Un and the giant statues, chanting "Mansei (long live)" for the ruling Kim dynasty.

"All party members and troops should hold the respected comrade Kim Jong-Un in high esteem...and protect him with our lives under any circumstances," Kim Yong-Nam said.

"Let's firmly rally behind the party centre led by the great comrade Kim Jong-Un...and vigorously fight!" he said, drawing thunderous applause from the crowds.

Giant balloons painted with national and party flags were hovering in the air, draping banners written with slogans reading "Solidarity and unity!", while troops fired celebratory gun rounds.