The governor of Russia's second city has signed a new law against "homosexual propaganda", in defiance of protests that it discriminates against gay people.
St Petersburg governor Georgy Poltavchenko signed the law - which promises fines for anyone found to have spread gay propaganda among minors - after it was adopted by the local legislature, AFP reports.
A regional law that applies only to St Petersburg, it will come into force 10 days after official publication.
Human rights groups had called on Mr Poltavchenko to veto the law on the grounds that it appears to equate homosexuality with paedophilia and risks being used arbitrarily by the authorities to crack down on gay people.
Any person found "making public actions among minors for the propaganda of homosexuality, lesbianism, bisexuality or transgenderism" will be subject to a fine of 5000 roubles, rising to 500,000 roubles for organisations.
Another article states that people "making public actions for the propaganda of paedophile" will be fined 5000 roubles, a sum that rises to one million roubles for organisations.
Maria Efremenkova, a leading gay rights activist who has organised Gay Pride rallies in the city, said they would "fight this discrimination".
She said that once the law comes into force later in March activists would hold protests near schools brandishing signs like "homosexuality is also natural" to test the law.
"This is so that legal proceedings are launched against us and we can then fight against the law in court."
It remains unclear how authorities will implement the law in what is Russia's top destination for foreign tourists and its vagueness has caused international concern.
"The bill's language is so vague and broad that it could lead to a ban on displaying a rainbow flag or wearing a T-shirt with a gay-friendly logo or even on holding LGBT-themed rallies in the city," Human Rights Watch said in a statement earlier in March.
"The bill is setting a dangerous precedent by maliciously linking paedophile with homosexuality."
Similar laws have also been approved in the regions of Ryazan and Kostroma outside Moscow and Arkhangelsk in the Far North. The authors of the St Petersburg law have vowed to bring a similar initiative to the federal State Duma parliament for adoption nationwide.
Homosexuality was decriminalised in Russia in 1993.