Putin signs a law banning expressions of L.G.B.T.Q. identity in Russia.

President Vladimir V. Putin of Russia intensified his crackdown on L.G.B.T.Q. people on Monday, when he signed new legislation that widely bans public expression of their identity in the country.

The new law makes it illegal to spread “propaganda” about “nontraditional sexual relations” in the media, advertising, movies or on social media. It had passed the Duma, Russia’s Parliament, by a vote of 397 to 0 on Nov. 24.

Demonstrations of “nontraditional relationships or preferences” will also be completely barred from advertising, and from any outlet visible to minors. Distributing to minors any information “that causes children to want to change their sex” was also prohibited.

The law is likely to put another strain on a community that has already been largely stigmatized in a country where officials have cast the repression of L.G.B.T.Q. expression as part of a wider struggle to protect Russia from Western interference.

Mr. Putin has long cast L.G.B.T.Q. life as a Western intrusion into Russia’s traditional society and values, and proponents of the new law recently likened the fight against L.G.B.T.Q. expression to Russia’s military actions in Ukraine, which they see as a broader civilization clash between them and the West.

“We have our own way of development; we do not need European imposition of nontraditional relations,” Nina Ostanina, chairwoman of the committee on family, women and children, said during parliamentary hearings on the legislation.