The financially troubled Gulf emirate of Dubai yesterday opened the world's tallest building, a glistening concrete, glass and steel pinnacle rising 828 metres out of the desert sands.

Blazing fireworks rippled up and down the massive structure after it was officially opened by Dubai ruler Sheikh Mohammad bin Rashed al-Maktoum.

He renamed the building, previously known as Burj Dubai, Burj Khalifa in honour of United Arab Emirates President Sheikh Khalifa bin Zayed al-Nahayan.

Sheikh Khalifa is also ruler of Abu Dhabi, the emirate which came to Dubai's help late last year to the tune of $10 billion to bail out troubled property developer Nakheel, a subsidiary of Dubai World.

"Today the United Arab Emirates achieves the tallest building ever created by the hand of man... and this great project deserves to carry the name of a great man. Today I inaugurate Burj Khalifa," Sheikh Mohammad said.

Parachutists bearing the UAE colours of red, green, black and white then touched down as a giant portrait of Sheikh Khalifa was projected on an outer wall of the structure which cost $1.5 billion to erect.

In the fireworks spectacle that followed blossoms of flames crackled up and down the huge building and out into the Dubai night sky, followed later by lasers sweeping the horizon from the tower's many levels.

Dubai hopes the opening of the Burj Khalifa - the latest in a series of grandiose projects - will burnish an image tarnished by its crippling debt woes.

The needle-shaped tower, described by its developer as a "vertical city" as it dwarfs existing skyscrapers, boasts new limits in design and construction.

Emaar Properties, the partly government-owned developer, had maintained the suspense about the skyscraper's final height, saying only that it exceeded 800 metres.

Yesterday it said the tower has more than 200 floors, only 160 of which will be inhabited, while the remaining floors are for services.

Burj Khalifa has a total built-up area of 5.67 million square feet, including 1.85 million square feet of residential space and more than 300,000 square feet of prime office space, Emaar said.