North Korea celebrated the birthday of late ruler Kim Jong-Il Monday with mass fireworks, high-ranking military promotions and a rally by senior officials to pledge loyalty to current leader Kim Jong-Un.

To mark the February 16 date, Kim Jong-Un promoted dozens of top military officers on Sunday and paid a midnight visit to the mausoleum housing his father's embalmed body, the North's state-run KCNA news agency said.

Accompanied by a large group of senior party and military, Kim bowed deeply and in "the humblest reverence" as he paid homage at the Kumsusan Palace of the Sun.

The capital Pyongyang also staged massive fireworks Sunday night to celebrate what is known as the "Day of the Shining Star".

The anniversaries of the births and deaths of Kim Jong-Il and his father, the country's founding leader Kim Il-Sung, are major holidays on the annual North Korean calendar.

In a statement to coincide with Monday's anniversary, US-based Human Rights Watch said Kim Jong-Il, who would have been 73, should be remembered for presiding over one of the world's "most brutal and repressive" governments.

During his 17-year rule, "Kim presided over the country's worst famine and oversaw systematic crimes against humanity against his own people", the rights monitor said.

Kim died in December 2011 and was succeeded by Kim Jong-Un.

Thousands of senior military and party officials gathered in a large auditorium in Pyongyang on Sunday to vow loyalty to the Kim dynasty.

During the meeting aired on state TV, Choe Ryong-Hae, one of Kim's closest aides and general secretary of the Central Committee of the Workers' Party, urged officials to protect the young leader with their lives.

In a keynote speech Choe praised Kim Jong-Il for promoting nuclear-armed North Korea "to the echelon of the world's top military powerhouse."

"All party members and people should continue to follow the steps of the great general (Jong-Il)... under the guidance of comrade Kim Jong-Un," he said.

The audience sat under a massive banner reading "The great leader Kim Jong-Il is always with us."

The Kim dynasty has ruled the isolated state for nearly seven decades with an iron fist and pervasive personality cult.

Kim Jong-Un, in his early 30s, is reputed to enjoy a luxury lifestyle of yachts, parties and gourmet food -- in a stark contrast to the poverty prevalent among his 25 million people.

Over the weekend, Kim flew over Pyongyang in his private jet for an aerial inspection of a residential complex being built for the country's top scientists.

KCNA images showed Kim staring out over the capital from the sleekly opulent interior of the plane -- a recently purchased Antonov An-148.

Unlike his father, who hated planes and would only travel overseas by train, Kim seems to have something of a passion for air travel.

Pyongyang has undergone a construction boom under Kim Jong-Un, and KCNA quoted him speaking of a "face-lift" for the capital that would turn it into a "world class city to be envied by the world."