Kirill Kudryavtsev / AFP - Getty Images

At least 20,000 people rallied Sunday on the Boulevard Ring in Moscow to oppose Vladimir Putin's law banning American adoptions of Russian children.

Thousands of people marched through Moscow on Sunday to protest Russia's new law banning Americans from adopting Russian children, a far bigger number than expected in a sign that outrage over the ban has breathed some life into the dispirited anti-Kremlin opposition movement.

Shouting "shame on the scum," protesters carried posters of President Vladimir Putin and members of Russia's parliament who overwhelmingly voted for the law last month. Up to 20,000 took part in the demonstration on a frigid, gray afternoon. 

The adoption ban has stoked the anger of the same middle-class, urban professionals who swelled the protest ranks last winter, when more than 100,000 people turned out for rallies to demand free elections and an end to Putin's 12 years in power. Since Putin began a third presidential term in May, the protests have flagged as the opposition leaders have struggled to provide direction and capitalize on the broad discontent. 

Opponents of the adoption ban argue it victimizes children to make a political point. Eager to take advantage of this anger, the anti-Kremlin opposition has played the ban as further evidence that Putin and his parliament have lost the moral right to rule Russia. 

The Kremlin, however, has used the adoption controversy to further its efforts to discredit the opposition as unpatriotic and in the pay of the Americans. 

UNICEF estimates there are about 740,000 children not in parental custody in Russia, while about 18,000 Russians are on the waiting list to adopt a child. Since the law banning American adoptions was passed, Russian political and religious leaders have been encouraging Russians to adopt more children.

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Sunday's march may prove only a blip on what promises to be a long road for the protest movement, especially in the face of Kremlin efforts to stifle dissent. But it was a reunion of what has become known as Moscow's creative class, whose sarcastic wit was once again on display on Sunday. 

"Parliament deputies to orphanages, Putin to an old people's home," read one poster. Another showed Putin with the words "For a Russia without Herod." 

Putin's critics have likened him to King Herod, who ruled at the time of Jesus Christ's birth and who the Bible says ordered the massacre of Jewish children to avoid being supplanted by the newborn king of the Jews. 

Russia's adoption ban was retaliation for a new U.S. law targeting Russians accused of human rights abuses. It also addresses long-brewing resentment in Russia over the 60,000 Russian children who have been adopted by Americans in the past two decades, 19 of whom have died. 

Cases of Russian children dying or suffering abuse at the hands of their American adoptive parents have been widely publicized in Russia, and the law banning adoptions was called the Dima Yakovlev bill after a toddler who died in 2008 when he was left in a car for hours in broiling heat. 

"Yes, there are cases when they are abused and killed, but they are rare," said Sergei Udaltsov, who heads a leftist opposition group. "Concrete measures should be taken (to punish those responsible), but our government decided to act differently and sacrifice children's fates for its political ambitions." 

Those opposed to the adoption ban accuse Putin's government of stoking anti-American sentiments in Russian society in an effort to solidify support among its base, the working-class Russians who live in small cities and towns and who get their news mainly from Kremlin-controlled television. 

Putin has turned his back on the new Internet generation in Moscow and other large cities, exacerbating a divide in Russian society that seems likely only to deepen in coming years. 

Protests against the adoption ban were held Sunday in a number of other Russian cities, but in most places only a few dozen people took part. In St. Petersburg, about 1,000 people turned out to show their opposition to the law and to Putin. Some held up a poster that read "Don't play politics using children." 

At the end of the protest, marchers dumped the posters of Putin and parliament members in an industrial-sized trash container that had "for disposal" scribbled on it. 

Sunday's protest had been authorized by the city government, which contributed to the high turnout. 

Just ahead of the weekend demonstration, Putin's spokesman sought to ease anger over the adoption ban by announcing that some of the dozens of adoptions already under way could go forward, allowing children who have already bonded with American adoptive parents to leave the country.  

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