Russian campaigners have said that a woman found murdered with multiple stab wounds in the city of Saint Petersburg was a well-known activist who had received threats over her protests for LGBT rights and opposition causes.

Authorities said they had found the body of a 41-year-old woman with multiple knife wounds in St Petersburg on Sunday, but did not identify her.

Activists and media reports in the city named the victim as local campaigner Yelena Grigoryeva, who was a regular participant in rallies supporting a range of unpopular causes in modern Russia, including LGBT rights and freedom for Ukrainian political prisoners.

“An activist of democratic, anti-war and LGBT movements Yelena Grigoryeva was brutally murdered near her house” on Friday night, opposition campaigner Dinar Idrisov wrote on Facebook. He said she had recently reported threats of violence to the police, but they took no action.

Acquaintances said Grigoryeva’s name was on a list of LGBT activists published by a recently blocked Russian website that called on people to take vigilante action against them. Russia’s internet watchdog banned the website last week.

In recent days, activists at an LGBT resource centre in the city of Ekaterinburg said they had received a threatening letter, signed by “a liquidator of gays”, warning that if they did not close down the centre “something very bad and very sad” could happen.

Photographs posted to Grigoryeva’s Facebook page in recent months showed her holding placards at various rallies and protests. One called for “A Russia which people will not be scared of, but be inspired by”. Another read: “In Russia there are more than 5 million gay people. Because of backwardness and hatred, they have to live secretly.”

Idrisov wrote that her views had changed over time, from nationalist to liberal, and said he did not know if the attack was related to her work. He said, however, that she had recently received threats and had even asked a friend to look after her cat in the event that anything happened to her.

The Saint Petersburg online newspaper Fontanka said Grigoryeva was found with knife injuries to her back and face and had apparently been strangled. A suspect had been arrested, it reported.