MOSCOW — As children gathered at a holiday camp outside Moscow, they were greeted by a female performer in a kokoshnik, a traditional tiara, who extended the customary Russian greeting of a loaf of bread and salt.

The children were not from Russia. They were Ukrainian children brought to the camp from Russian-occupied areas of Ukraine. “We welcome you like this,” said Maria Lvova-Belova, Russia’s commissioner for children’s rights, who was at the event, “because now you are ours.”

Many of the children Ms. Lvova-Belova has brought from Ukraine have indeed become Russian, at least by passport, thanks to a decree she asked President Vladimir V. Putin to sign last year to streamline the adoption of Ukrainian children.

She has used that authority to transfer to Russia what Ukraine says are as many as 16,000 children. Some of those children have described a wrenching process of coercion, deception and force, with many placed in homes to become Russian citizens and subjected to re-education.

She is reviled in Ukraine, where she is labeled a war criminal, and the United States and Britain imposed sanctions on her in 2022, but at home, Ms. Lvova-Belova is portrayed as the archetype of the woman revered in Mr. Putin’s Russia: a conservative, deeply religious mother to a large brood — as well as a dedicated advocate of the rights of children and people with disabilities.

In the Kremlin’s telling, she is far from a war criminal, instead leading a humanitarian evacuation of only around 2,000 orphans and other children who have been abandoned. The Russian propaganda machine notwithstanding, there is little doubt that she is a mother and guardian to many children: At the time of her appointment in October 2021, she told Mr. Putin that she had nine children, five biological and four adopted, while fostering 13 more. Now, her official biography lists her as the mother of 10 children, as she adopted a teenage boy from Mariupol, Ukraine, over the summer.

Ms. Lvova-Belova, 38, grew up in Penza, Russia, a city of about a half-million about 400 miles southeast of Moscow. She met her husband, Pavel Kogelman, when she was a teenager singing in a church choir. In high school, she studied conducting, and she later gave guitar lessons.

For more than a decade, Ms. Lvova-Belova threw herself into helping disadvantaged children and disabled people. One of her first public projects was to provide care for babies who had been abandoned by their parents.

In 2008, already the mother of two children, she co-founded an organization called Blagovest that helped orphans adapt socially. Her co-founder, Anna Kuznetsova, became something of a trailblazer for Ms. Lvova-Belova, first establishing a name for herself in the social services field and then branching into politics.

Both women became well known in the city for their efforts, said Oleg Sharipkov, the executive director of the Penza Civil Union Foundation. After establishing Blagovest, the two women went their separate ways as partners, with Ms. Lvova-Belova focusing on disabilities and Ms. Kuznetsova becoming active in the anti-abortion movement, but they remained close friends.

They had a good reputation in the community. They really, really, did some good things,” said Mr. Sharipkov. And then there was a “turning point,” he said, when both women realized that they could raise substantial funds from the regional and federal governments: “Both began to cuddle up hard to power.”

In July 2014, Ms. Lvova-Belova founded a nongovernmental organization called the Louis Quarter, after the jazz musician Louis Armstrong, a center for orphans with disabilities who had aged out of state homes but were not yet prepared for independent living. She said she chose Armstrong because he rose so far after starting from deprived circumstances.

Ms. Kuznetsova, who had become the head of Mothers of Russia, a government-aligned group promoting traditional values, was appointed commissioner for children’s rights in 2016. That opened a door to bigger projects for Ms. Lvova-Belova. She started several group homes for people with severe disabilities, including one called New Shores that grew into the largest assisted-living center for disabled Russians.

In September 2019, a month after her husband was ordained a Russian Orthodox priest, Ms. Lvova-Belova was elected to the Penza City Duma, or Parliament, as a candidate of Mr. Putin’s United Russia Party. But in a common practice that allows the party to choose its own lawmakers, she refused the seat, clearing the way for a party pick who was less well known. She was rewarded with a significant jump in her career. A month later, Dmitri A. Medvedev, the former president of Russia and chairman of United Russia, formalized her place with a party membership card. The next day, she became a member of United Russia’s presidium, the 35 people who manage the party.

I think when they used to work, they genuinely believed they were doing good things, and then at some point they made a compromise: To get money for the project, you have to go to the polls,” said Mr. Sharipkov of Ms. Lvova-Belova and Ms. Kuznetsova. “Just like this, little by little. It’s just pure politics right now.”

A year later, in September 2020, the party gave her a seat as a senator in the Duma’s upper house, the Federation Council. When Ms. Kuznetsova stepped down as children’s rights commissioner in autumn 2021, Ms. Lvova-Belova was appointed in her place.

Ms. Lvova-Belova met with Mr. Putin for the first time on March 9, 2022, in a session that was videotaped and made public. It had been less than two weeks since Russian troops’ full-scale invasion of Ukraine, but she told the president that 1,090 orphans had already arrived.

“Of course, Russians have big hearts and are already queuing up to take care of these children. What do you think?” she asked, adding that only those who had Russian documents could settle permanently into families.

There were “legal caveats” to be addressed before non-Russian children could be adopted, she told Mr. Putin, who quickly brushed aside such concerns. “We are facing an emergency,” he said. “I believe that we must focus on the interests of the children rather than think about red tape.”

In May, Mr. Putin issued a decree that removed the obstacles to giving the children Russian passports.

Having been given her marching orders, Ms. Lvova-Belova began traveling to the Russian-occupied areas of Ukraine, visiting orphanages, bringing supplies and often bringing children back with her. In mid-July, she posted on the Russian social network VKontakte that 108 children of the Donbas region would receive citizenship that week. As she dropped a group of them off with their foster parents, she wiped away tears.

But Ms. Lvova-Belova stands accused of serious violations of international law, such as extracting children from orphanages and hospitals in Russian-occupied areas of Ukraine even though many had relatives who would have taken them in.

Researchers affiliated with Yale University reported that she used a network of summer camps spanning at least eight time zones, from the annexed Crimean Peninsula to Magadan, in Russia’s far east, to move Ukrainian children to Russia. While Russia was occupying parts of Ukraine’s Kharkiv and Kherson regions, families there were promised a two-week summer vacation in Russia for their children as a break from the hostilities. But when Ukraine reclaimed the areas in September, many of the children had not been able to leave the camps in Russia and were still stranded there.

In early March, Ms. Lvova-Belova acknowledged in a post on Telegram that 89 children in the summer camps were waiting to go home, but she denied that they or any others were being held against their wishes.

“If parents or legal guardians are able and willing to take them in, we do everything in our power to help them,” she said, adding that she had not received an official request from the Ukrainian authorities “regarding this group of children.”

This professed willingness to return the children is hotly disputed in Kyiv, Ukraine’s capital, where the authorities say that only 327 Ukrainian children out of the thousands Russia has extracted have been returned. Ukraine’s ombudsman, Dmytro Lubinets, told The New York Times in a recent interview that the Ukrainian authorities had never been given a list of children who were taken to Russia.

Despite the accusations against her, the sanctions and the international warrant for her arrest, Ms. Lvova-Belova has defiantly supported her actions.

“I arrived in hell,” she told the pro-government, conservative channel Tsargrad about her first journey to Mariupol, in an interview broadcast in November. “I’m honestly not ashamed of this year. I’m not ashamed because I think my team worked not 100 percent, but 150 percent.”