President Vladimir V. Putin approved the adoption ban in late December as part of a broader law retaliating against the United States for the so-called Magnitsky Act, an effort to punish Russian officials accused of human rights violations.

Russian leaders have complained bitterly for years about what they consider light sentences in cases where American parents abused or neglected children adopted from Russia, and named the ban after Dmitri Yakovlev, a toddler who died of heatstroke in Virginia in 2008 after his adoptive father left him in a parked car for nine hours.

But the decision has proved to be controversial in Russia, even within government circles. More than 650,000 children live in foster care or orphanages in Russia, of whom about 120,000 are eligible for adoption. Many children in orphanages are sick or disabled, and most have little hope of finding permanent homes.

“We hope that these people, who came out to express their opinion, are aware of the plans of our nation’s leaders to bring order to the adoption process, and the implementation of a range of measures aimed to improve the lives of orphans,” said Dmitri S. Peskov, the Kremlin press secretary.

The protesters on Sunday, however, were not likely to be convinced. One woman carried a sign that said, “Stop the repressions, you’re making revolutionaries out of us.” Many said they supported the Magnitsky Act, which American lawmakers passed late last year, as a way to hold Russian officials accountable for crimes that would otherwise never be punished.

“I truly think they have lost touch with society, and they use these laws to divert society’s anger toward ‘our enemies,’ the Americans,” said Boris Komberg, a physicist who was distributing a poem he had written about the adoption issue.

Yelena Rostova, 61, said anger over the ban had caught the authorities by surprise.

“They expected that, as usual, we would swallow it, keep quiet,” Ms. Rostova said. “We have had two weeks to think about this law, and not everyone understood right away, but as time passed, people realized what it means to leave invalids, sick children, in Russia, where there is no help. Everyone knows what kind of medicine we have here.”