Image copyright Getty Images Image caption The arrested people (not pictured) were said by a law official to be wearing inappropriate outfits

Thirty people taking part in a yoga session have been arrested during a private class in Iran, reports suggest, causing a buzz across the country's social media.

They were detained at a private residence in the northern city of Gorgan, where they were apparently taking part in a mixed class.

Local justice department official Massoud Soleimani said the instructor, who was also arrested, had no licence to run the class and had advertised the event on Instagram.

He also said that those taking part were wearing "inappropriate outfits" and had "behaved inappropriately", the Tasnim news agency reports.

The Islamic establishment in Iran does not allow any mixed-gender sports activities.

Professional-level yoga teaching is also banned in the country.

Mr Soleimani, the deputy chief of the Islamic Revolution Court in Gorgan which is the capital of Golestan Province, did not give any more details about the attire or behaviour of the detained group.

He did say that security forces had been monitoring the residence for some time before making the arrests.

Cancelled classes

The story, which was also reported by the Young Journalists Club, has caused a stir online and has become a top trending topic in social discussions.

"They [Iranian authorities] think even the word yoga is problematic based on the Sharia," one user tweeted.

"An establishment that finds even yoga harmful does not need the USS Abraham Lincoln warship to end its existence," another tweeter added, referring to the recent deployment of US warships to the region.

Others say they have cancelled their plans to sign up to yoga classes following the arrests in Gorgan.

"I guess the authorities need to tell us what exactly we are allowed to do in this country," commented another tweeter.

In 2017, Iranian sports authorities issued a ban on Colombian dance aerobics exercise zumba and "any harmonious movement or body-shaking instruction".

Back then Iran's Sport for All Federation penned a letter to Iran's Ministry of Youth Affairs and Sports to ban activities, including zumba, for contravening "Islamic ideology".

While there have have been public gatherings of yoga fans in the country over the past few years, "underground" and "unIslamic" classes, which are promoted across social media, are frowned upon.

While revealing the arrests, Mr Soleimani also criticised the "lack of surveillance of activities" on social media in the country.

Twitter is officially banned in the country. However, there does appear to be an increased surveillance of Instagram by Iran's authorities, especially more recently.

This week the social media accounts of at least three street musicians were apparently seized by Iranian authorities for publishing "criminal content", while singer Negar Moazzam is currently under investigation after performing for a group of tourists in the country's Isfahan Province.

Her Instagram account is no longer public.

BBC Monitoring contributed to this report