Egyptian police have arrested seven people after they were allegedly seen raising rainbow flags at a concert in Cairo last week, security sources say.
The seven were reportedly detained on Monday for "promoting sexual deviancy", but have not yet been formally charged.
Prosecutors opened an investigation after images from the concert by the Lebanese band Mashrou' Leila - whose lead singer is openly gay - went viral.
Homosexuality is not explicitly criminalised under Egyptian law.
But the authorities routinely arrest people suspected of engaging in consensual homosexual conduct on charges of "debauchery", "immorality" or "blasphemy".
The advocacy group, Solidarity With Egypt LGBTQ+, said late last year that it had recorded 114 criminal investigations involving 274 lesbian, gay, bisexual and transgender individuals since 2013.
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The raising of the rainbow flag was a rare public show of support for the LGBT community in the conservative Muslim country.
Late on Monday, the state news agency reported that Public Prosecutor Nabil Sadek had ordered an investigation by the State Security Prosecution after images posted on social media were condemned by several politicians and media figures.
The deputy head of the Egyptian Musicians Syndicate, Reda Ragab, meanwhile said it would be taking steps to stop Mashrou' Leila performing again in the country.
"We are a religious, conservative society, an identity we need to preserve," he told the Daily News Egypt website.
"This is a scandal against our traditions and far from serious and meaningful art."
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The Egyptian feminist and writer Mona Eltahawy condemned the actions of both the authorities and the musicians syndicate.
"It is utterly ridiculous to arrest anyone for waving a flag. It is utterly ridiculous to arrest anyone for their sexuality as #Egypt does," she wrote on Twitter.
Mashrou' Leila has twice been banned from performing in Jordan. On Saturday, it said the Cairo concert "was one of the best shows we've ever played".
"Was an honour to play to such a wonderful crowd! So much love!"