Russian MPs has backed a ban on the promotion of homosexuality among children.
Police made arrests outside the State Duma in Moscow after gay rights supporters planning a "kiss-in" were assaulted by opponents.
The bill echoes laws passed by Russian cities such as St Petersburg.
Human rights campaigner Lyudmila Alexeyeva said its real aim was to "curb the rights of sexual minorities".
The bill faces two more readings in the State Duma, after which it must be approved by the upper house (Federation Council) and President Vladimir Putin before it can become law.
If passed, it would mean that across Russia events promoting gay rights would be banned and the organisers fined.
Under the new bill, private individuals promoting "homosexual behaviour among minors" in Russia face fines of up to 5,000 roubles (£105; 124 euros; $166) while officials risk paying 10 times that amount. Businesses and schools could be fined up to 500,000 roubles.