MOSCOW — Russia’s upper house of Parliament moved to strengthen controls over the Internet and nonprofit organizations on Wednesday, prompting a warning from the United Nations human rights chief that the Kremlin is sliding back into Soviet ways.

A series of initiatives have been introduced as President Vladimir V. Putin begins a six-year term, facing an increasingly assertive opposition. The government has imposed draconian fines for people who participate in unsanctioned protests, and legislators voted to reinstitute criminal charges for slander, rolling back a reform adopted seven months ago by Dmitri A. Medvedev, Mr. Putin’s predecessor.

The bills approved on Wednesday would allow the government to block Web sites deemed dangerous to children and require nonprofits to identify themselves as “foreign agents” if they receive financing from outside Russia and are considered by the government to be engaged in political activities.

“In just two months, we have seen a worrying shift in the legislative environment governing the enjoyment of the freedoms of assembly, association, speech and information in the Russian Federation,” said Navi Pillay, the United Nations high commissioner for human rights, in a statement released in Geneva.