Russia's parliament passed a bill banning homosexual "propaganda" on Tuesday (June 11) while police detained more than 20 gay rights activists outside.

The State Duma, or lower house of parliament, passed the bill in two readings with only one deputy abstaining from vote, ignoring Western criticism that it curbs basic freedoms and concerns among activists that it is fuelling hate attacks on homosexuals.

The bill would ban the spread of "propaganda of non-traditional sexual relations" among minors and impose heavy fines for violations.

Critics says the bill - a nationwide version of laws already in place in several cities including Putin's hometown of St Petersburg - would in effect ban all gay rights rallies and they fear it could be used to prosecute anyone voicing support for homosexuals.

The 60-year-old president denies that Russia discriminates against gays but he has criticised them for failing to increase the country's population, which has declined sharply since the collapse of the Soviet Union in 1991.

Activists say violence against homosexuals has increased since Putin returned to the Kremlin after four years as prime minister and that it is being fuelled by the bill and other aspects of his conservative agenda.

It is unusual for Russian authorities to link crimes with homophobia, but investigators have said anti-gay hate was the motive in the brutal murders of two men in the past month, one in eastern Russia and one in the southern city of Volgograd.