Two international rights groups have called on Egyptian authorities to end their crackdown on people suspected of homosexuality and to “immediately and unconditionally” release at least 11 men detained in the past week.

The latest crackdown began after a group of people were seen raising a rainbow flag at a September 22 concert in a rare display of support for the lesbian, gay, bisexual, and transgender communities in the conservative Muslim-majority country of 95 million people.

While taboo in Egypt, homosexuality is not explicitly banned by law, but gay men are often arrested in police raids on private parties, public baths, restaurants, and bars.

Charges are usually officially listed as “promoting sexual deviancy" and "debauchery."

The two rights groups, Human Rights Watch and Amnesty International, said 11 people have been arrested after social media footage showed the rainbow flag being raised at a September 22 concert by Lebanese rock band Mashrou' Leila. The group’s singer is openly gay.

"These men should be released immediately and unconditionally — not put on trial," said Najia Bounaim, Amnesty's North Africa Campaigns Director.

"A sinister smear campaign by Egyptian media against those believed to have raised the rainbow flag at the Mashrou' Leila concert, has given security forces a green light to carry out arrests of at least 11 people based on their alleged sexual orientation," Bounaim said.

Based on reporting by AP and Reuters