Indian Prime Minister Narendra Modi left many confused when he finished a speech to the music of Darth Vader's Imperial March from the Star Wars saga.

Addressing a crowd at the Institute of Chartered Accountants on Saturday, Mr Modi introduced the new Goods and Services Tax, which has been described as the biggest tax reform since the country became independent 70 years ago.

Psyching up a crowd at New Delhi's Indira Gandhi Stadium for a spiel on tax reformation is a hard task — which could explain the Prime Minister's soundtrack choice.

Mr Modi closed his speech by waving to the crowd as the Imperial March boomed across the stadium.

What seemed like Mr Modi trying to liven up his speech, caught viewers around the country by surprise.

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But the finale was not the first time Mr Modi referenced the sci-fi series of films. The Prime Minister ended a speech at Central Park, New York, in September 2014 by wishing the crowd: "May the force be with you."

Star-studded tax announcement

The introduction of a nationwide goods and services tax was marked by a star-studded event.

It was first proposed under a previous congress-led government but it has been realised by the current Prime Minister, who has promised dramatic reform to support business and boost the economy.

Supporters say it unifies India in a single market, will help to tackle corruption and force more businesses to comply with tax rules.

Opponents say it is an extra burden for many small traders and they predict a bumpy road ahead.