Moscow (AFP) - Russian state television has provoked a storm of criticism after it aired an uncorroborated report claiming that the Ukrainian army publicly nailed a three-year-old boy to a board in a former rebel stronghold.

Ukraine accused Russia of ratcheting up its propaganda war by airing an interview in which a woman gave graphic details of the alleged incident in the Ukrainian flashpoint city of Slavyansk, which neither AFP nor other media have been able to confirm.

Channel One television at the weekend broadcast footage of a woman who said she recently saw Ukrainian soldiers round up people in central Slavyansk, which the army took over this month after three months of clashes with separatists, and nail an insurgent's child to a notice board.

A spokeswoman for Ukraine's interior ministry, Natalya Stativko, on Monday slammed the report as "following in the footsteps of Goebbels," Nazi Germany's minister of propaganda.

"The cruder and the more monstrous the lie, the better it will look for the Russian propaganda machine," Stativko told AFP.

Galina Timchenko, former editor of Lenta.ru, a prominent news portal in Moscow, said the report was a gross breach of professional ethics by one of Russia's most watched channels.

"This is an egregious violation of professional ethics," she told AFP.

"Not only is there no proof anywhere -- this is not even being questioned."

Opposition leader Alexei Navalny denounced the channel as "nutty" for airing the report.

"Are they completely sick to be concocting this?" he wrote on his blog. "The people behind this are a danger to society and what they are doing is a true crime."

Representatives of Channel One declined immediate comment.

The report featured a woman named as Galina Pyshnyak, who was interviewed at a refugee camp in Russia, describing the incident that she labelled an act of revenge.

"They gathered women on the square because there are no more men. Women, girls, old people," Pyshnyak said.

"They took a child of around three years old, a little boy in his underwear and a T-shirt and nailed him to a notice board like Jesus. One was nailing him and two others holding him."

Russian official rhetoric often compares events in Ukraine to Nazi Germany and calls the pro-Western Kiev government a "fascist junta".