Iranian authorities have freed a group of music fans who were arrested for filming a video of themselves dancing to Pharrell Williams' hit song Happy.

Three men and three women were tracked down and taken into custody on Tuesday (20May14) after a clip of the friends' promo tribute, featuring them dancing on the streets and rooftops of Tehran, became a viral hit after it was uploaded onto YouTube.com last month (Apr14).

The city's police chief Hossein Sajedinia branded the footage "vulgar" and demanded the arrest of the fans and those involved in the shooting of the video.

The news caught Williams' eye and he expressed his disdain at their imprisonment in a message online, which read: "It is beyond sad that these kids were arrested for trying to spread happiness."

Iran's president Hassan Rouhani also appeared to criticise the cops' actions by reposting a tweet he previously wrote last year (13). It read: "#Happiness is our people's right. We shouldn't be too hard on behaviours caused by joy."

The six video stars have since been released on bail, and one of the women, fashion photographer Reihane Taravati, took to her Instagram.com account on Wednesday (21May14) to thank fans for their support.

She writes, "Hi, I'm back... thank you @pharrell and everyone who cared about us love you all so much and missed you so much (sic)".

However, a representative for the International Campaign for Human Rights in Iran (Ichri) reveals not all those arrested are free.

A message shared on the organisation's Twitter.com page reads: "All people who made the Happy video released today, except the director of video, a source close to the families said."