Police in Iran have released six people who were arrested for posting a video online of them dancing to US pop-star Pharrell Williams' hit song "Happy", reports said.

Media reports from Tehran on Wednesday suggested that authorities had released the group who filmed the short video of them dancing on a rooftop, a stairwell, a walled-off driveway and in an apartment, while laughing and smiling, with the audio set to the popular song.

State media showed an interview with Tehran's police chief, calling the video a vulgar clip which hurt public chastity. 

But Iranian President Hassan Rouhani's official Twitter account posted a message in support of the group on Wednesday: "Happiness is our people's right. We shouldn't be too hard on behaviours caused by joy."

It was not immediately clear if the six arrested faced criminal or civil charges or had lawyers, but reports suggested they were released on bail. However, the International Campaign for Human Rights in Iran group tweeted that the director of the video was still in custody, citing a source close to their families.

One member of the group posted a photo of herself on Instagram, thanking those who called for her release.

The women in the video do not wear hijabs. Laws in Iran ban women from dancing in public or appearing outside without the hijab, the Associated Press news agency reported.

Williams' song had become a global sensation, sparking similar videos from more than 140 countries, with people dancing down streets and smiling in choreographed crowds.

On Twitter, Williams posted a link to a story about the arrests and wrote late on Tuesday: "It's beyond sad these kids were arrested for trying to spread happiness."

The arrest of the group sparked a Twitter campaign with the hashtag #FreeHappyIranians.

Source: Al Jazeera And AP