German Chancellor Angela Merkel has urged Russian President Vladimir Putin to help protect gay rights.
Activists say police in the republic of Chechnya have arrested and tortured dozens of gay people in a crackdown.
Mrs Merkel raised the issue during her first visit to Russia since 2015, which saw her hold talks with Mr Putin at his summer residence in Sochi.
Relations between the two nations have been strained over Syria and Russia's annexation of Crimea from Ukraine.
At a tense joint news conference with Mr Putin, Mrs Merkel said she had received "negative reports on the treatment of homosexuals, particularly in Chechnya".
"I asked President Putin to use his influence to guarantee the rights of minorities," she added.
The news conference also saw:
- The two leaders urge the full implementation of the Minsk agreement, an internationally-brokered peace deal for Ukraine
- Mr Putin urge a "thorough and unbiased investigation" into the chemical weapons attack on a Syrian town last month
- Mr Putin insist that Russia "never interferes in the political life and the political processes of other countries - and we don't want anybody interfering in our political life and foreign policy processes"
- Mrs Merkel declare: "I am always of the view that even if there are serious differences of opinion in some areas, talks must continue"
Mr Putin is due to meet Turkish leader Recep Tayyip Erdogan later on Wednesday.
'It's the extermination of gay men'
Just a few weeks ago, "Ruslan" was with his wife and children in Chechnya. Now he's in a safe house for men fleeing detention and torture for being gay.
Reports of a campaign against gay men by Chechen security forces have been trickling through since early April when they first appeared in a Russian newspaper. Now some of the alleged victims are starting to speak out.
"When they brought me in, I denied everything," says Ruslan - not his real name. Even now, he is frightened of being identified.
Homophobia is widespread in Chechnya, a mainly Muslim region run by Ramzan Kadyrov, an authoritarian leader with a notorious private militia who is fiercely loyal to President Putin.
Last month, Natalia Poplevskaya of the Russian LGBT Network said there was "an organised campaign to detain gay men" in Chechnya.
Victims of the crackdown - who were either gay or just perceived to be gay - were being held at a detention centre near Argun, 20km (13 miles) from the city of Grozny, she said.
"Torture is going on with electric shocks, beatings with cables," she told the BBC, adding that three deaths had been reported. "All the people arrested are homosexual men or perceived as being gay."
A Chechen government spokesman, Alvi Karimov, denied the allegations.
"You can't detain and repress people who simply don't exist in the republic," he said.