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

The law, presented as a way to protect children by eliminating websites devoted to child pornography, pedophilia, illegal drug use and suicide, won broad support in the Duma, the 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, who 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 up to as much as the offender's annual income. 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 not only to remove the offending text but 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," he said.

Elena Kolmanovskaya, editor in chief of Yandex, Russia's largest search engine, said protection of children was as important as freedom of speech and access to information. But she said in a 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 them guilty. "It could be applied to all kinds of statements on the Web. And we do not have acquittals in our courts."