The impoverished ex-Soviet republic of Tajikistan has unveiled what is being billed as the world's tallest flagpole in a ceremony marking its 20th anniversary of independence.

"A thousand years on, the Tajik people have regained the independence and statehood they had sought all these years," Tajik President Emomali Rahmon said in a grand ceremony broadcast on all four state television channels.

The the 165-metre (541-foot) flagpole was built by the US company Trident Support, a firm that has also installed a 162-metre flagpole in Azerbaijan's capital Baku.

The 30 by 60 metre national tri-colour that sails at the top of the pole can be seen throughout the capital Dushanbe and is widely believed to be the largest in the world.

The poorest of the former Soviet republics has gone on a national spending spree ahead of the September 9 independence day holiday and earlier unveiled a five-metre national coat of arms that stands on top of a 45-metre base.

Officials did not disclose the cost of either project.

Construction of the flagpole began on November 24, 2010 when Tajikistan marked National Flag Day.