Dubai's ruler has opened the world's tallest building today, in a testament to the emirate's still strong ambitions to become a global business hub despite the debt problems that have dampened investor optimism.

Burj Dubai, whose opening has been delayed twice since construction began in 2004, marks another milestone for the deeply indebted emirate with a penchant for seeking new records.

Dubai, one of seven members of the United Arab Emirates, gained a reputation for excess with the creation of man-made islands shaped like palms and an indoor ski slope in the desert.

With investor confidence in Dubai badly bruised by the emirate's announcement in November that it would seek a debt standstill for one of its largest conglomerates, the Burj Dubai is seen as a positive start to the year after a bleak 2009.

The project has been scrutinised by human rights groups, who have objected to its treatment of labourers, as well as by environmentalists who said the tower would act as a power vacuum, increasing the city's already massive carbon footprint.

Developer Emaar Properties spent $1.5 billion on the tower since construction began in 2004.

The building's official height is 828 metres. The world's second-highest tower, Taipei 101 in Taiwan, stands at slightly above 500 metres.

Burj Dubai has 200 storeys of which about 165 are inhabitable and opens 1,325 days after excavation work started in 2004.

It took 22 million man hours to complete construction.

The tower contains 330,000 cubic metres of concrete, 39,000 m/t of reinforced steel, 103,000 square metres of glass and 15,500 square metres of embossed stainless steel.

The weight of the empty building is 500,000 tonnes.

Total built-up area is 526,760 square metres, of which 171,870 square metres is residential and 27,870 square metres is office space.

The structure will host the highest observation deck, swimming pool, elevator, restaurant and fountain in the world.

There are 900 residences available in addition to the soon-to-open Armani hotel. Owner Emaar said 90 percent of the building has been sold.

The building is covered by 24,348 cladding panels to help it withstand the UAE's summer heat.