Members of the State Duma, the lower parliament chamber, are seen during a session in Moscow, Russia on July 10, 2012. (Misha Japaridze/AP)

The Russian parliament passed a hastily introduced law Wednesday that allows the government to impose limits on the Internet, prompting fears that it could prove a first step toward censorship of a previously unbridled forum.

The measure, presented as a way to protect children by eliminating Web sites devoted to child pornography, pedophilia, illegal drug use and suicide, won broad support in the State Duma, or lower house, where 441 of 450 members voted for it.

Bloggers, media groups and human rights defenders opposed it, worried that it was not well thought out — it was introduced only last week — and could be loosely interpreted by the courts, which are seen as serving the interests of the authorities rather than observing the legal code.

Opposition groups, which have relied on the Internet to rally support, called it part of a broad assault on them. Last month, the Duma passed a law drastically raising fines for protesters who violate the rules for holding a demonstration. On Wednesday, it advanced a bill that would make slander a criminal offense, with a penalty of as much as the annual income of the offender. And it is expected to pass a law this week requiring nongovernmental organizations that do political work and get money from abroad to register as foreign agents.

“Many of us are now in danger,” said Oleg Kozyrev, an influential blogger. “I see this Internet law as part of a package of repressive laws directed at the opposition and human rights and civil rights activists.”

Under the new law, he said, a commenter could post a link to child pornography on a blogger’s page, for example, and the government would have the authority to close down the entire page. The page would remain closed while its owner attempted to prove he was not responsible for the illegal reference. “There is little hope that the courts or investigators will be objective,” Kozyrev said.

Elena Kolmanovskaya, editor in chief of Yandex, Russia’s largest search engine, said protection of children is as important as freedom of speech and access to information. But she said in an e-mailed statement that Yandex opposes the law, which requires creation of a blacklist of Internet sites.

“These amendments address very important issues and affect the interests of many parties: citizens, state and the Internet industry,” she said. “Decisions like this should not be made as hastily as it happened this time.”

The law is so broad that even vulgar language could be deemed an offense, said Alexander Morozov, a blogger and director of the Center for Media Research.

“Civic activists, journalists and politicians all have grounds to be nervous,” he said, observing that once authorities make their desires clear by charging someone, judges generally go along and find the defendant guilty. “It could be applied to all kinds of statements on the Web . And we do not have acquittals in our courts.”