Moscow's children's rights ombudsman and other public figures have reacted with outrage to Russian prosecutors' moves to remove a one-year-old boy from his parents because they allegedly took him to an unauthorised protest.

Prosecutors claimed Dmitri and Olga Prokazov endangered the child by taking him to the July 27 rally in the Russian capital that was violently dispersed by police, and that they handed him to another man who is now being sought on charges of organising mass riots.

The case follows a police crackdown on rallies protesting against the exclusion of opposition candidates from September's city council election.

Police detained more than 1,400 people during the July 27 protest and rounded up a further 1,001 during another demonstration on Saturday, according to an independent monitoring group.

Children's rights ombudsman Yevgeny Bunmovich denounced what he called "political blackmail involving children", and said he has written to Moscow's prosecutor urging him to drop the charges.

Members of the presidential human rights council also criticised the prosecutors' action, which comes amid a slew of criminal cases after the protests against the Kremlin.

Most of those detained were released within hours, but some have remained in custody and face criminal charges that may carry prison terms.

Speaking on independent Dozhd TV late on Tuesday, Mr Prokazov denied that the couple had taken part in the rally and said they had simply gone for a walk across central Moscow.

He said they were aware of the protest and sympathised with the demonstrators, but did not want to take part in it as they were walking with their child.

He insisted that they did nothing wrong by letting a close friend carry their child. The man is now being sought by authorities on charges of inciting riots, and investigators have claimed he used the child as a shield to cross police lines.

Mr Prokazov denied that, saying they were nowhere near police cordons and the boy was never in jeopardy.

"We didn't feel any danger," he said. "It never occurred to me that I was doing something wrong."

He and his wife said they were scared when police knocked on their door just before midnight, searching their apartment and treating them as if they were dangerous criminals.

"We were shocked. We felt as if some monsters wanted to take our child from us," he said. "It's barbaric."