North Korea celebrated the birth anniversary of late leader Kim Jong-il Sunday after promoting key military officials, including the chief of its rocket unit, state media has announced.

Kim Rak-gyom, the commander of the Korean People's Army (KPA) Strategic Rocket Force Command, was promoted to colonel general at the order of leader Kim Jong-un, the Korean Central News Agency (KCNA) reported late Saturday.

The unit is in charge of the country's mid- and long-range missile program.

Dozens of other senior military officials were also promoted to the rank of lieutenant general and major general, the KCNA said.

The latest round of military promotions, often announced on key political anniversaries, comes as the North celebrated Kim Jong-il's birthday.

The birthdays of both late leaders, with Kim Jong-il's on February 16 and his father Kim Il-sung's on April 15, are marked as major national holidays.

Thousands of party and military officials convened in the capital Pyongyang to pledge loyalty to Kim Jong-un, television footage showed on Sunday.

"Everybody, let's rally around the party center led by the great leader Kim Jong-un and robustly ... fight to complete the revolution!" the ceremonial head of state Kim Yong-nam said in a speech, which was given in  an indoor stadium.

The military promotions come after an analysis of new satellite images which was posted on the 38 North website showed stepped up excavation activity at the North's main nuclear test site, although there were no signs that any further test was imminent.

The Kim family has ruled the communist state for more than six decades through a pervasive personality cult and an iron fist.

To deal with the human rights issue in North Korea, after a year of investigation, the UN is set to release a detailed report on human rights violations in North Korea that could pave the way for criminal prosecution in an international court.

AFP - Reuters