Animal rights activists said Monday they would ask prosecutors to investigate an unsettling incident in which dead and wounded sheep were used in a smear campaign against the new liberal opposition movement Solidarity.

Delegates to Solidarity's founding congress over the weekend said unidentified men in a bus Friday dumped around 20 dead and dying sheep dressed in Solidarity T-shirts onto the ground in front of the hotel where the congress was held in the northern suburb of Khimki.

"There were two people in the bus who were throwing them out," said delegate Ella Polyakova, who witnessed the incident. "We started to yell at them, and they shouted back saying the same fate awaits us."

A video of the incident being circulated in the Russian blogosphere shows an ailing, whimpering sheep lying on its side atop what appear to be sheep corpses.

Polyakova said she called the police, who arrived and removed both dead and living sheep from the scene.

Irina Novozhilova, head of the animal rights group Vita, said her organization along with several others will ask the Prosecutor General's Office to open a criminal case in connection with animal cruelty.

"This is shocking to torture animals to achieve political goals," Novozhilova said. "Those who organized this disgusting act must be found and punished."

The incident bore the hallmark of the often bizarre stunts pulled by pro-Kremlin youth groups to disrupt opposition press conferences, congresses and demonstrations.

In the video, which was filmed by youth opposition activist Oleg Kozlovsky, a delegate says he recognizes one of the men dumping the sheep as an activist from Young Guard, the official youth wing of United Russia, whose leader is Prime Minister Vladimir Putin.

Young Guard spokesman Mikhail Dukhovich denied his group's involvement, saying they were against animal cruelty. A spokeswoman for Nashi, the most well-funded of the pro-Kremlin youth groups, also denied her group was involved.

One the men in the bus identified himself as Nikolai but refused to say who organized the stunt, Kozlovsky said.

"Of course no one will claim responsibility for such an action because it is criminal," Novozhilova said. "But there should be investigation."

Under the criminal code, cruelty to animals is punishable by up to two years in prison.

Delegates who witnessed the entire incident filed a complaint with Khimki police, Kozlovsky said.

A duty officer at Khimki police headquarters declined to comment by telephone. Khimki police spokeswoman Maria Ratnikova said she did not know if a criminal investigation had been opened or whether anyone was detained.

Animal rights activist Darya Taraskina, who runs several animal shelters throughout Moscow, said she also called police but was told there had been no incident involving sheep.