Russian opposition leader Aleksei Navalny and several members of his Anticorruption Foundation (FBK) were attacked by Cossacks at an airport in the southern Black Sea resort city of Anapa on May 17.
Videos show Navalny and about 30 FBK members walking toward the airport when they encounter a group of men wearing Cossack hats and uniforms.
Navalny and other FBK members are doused with milk and verbally berated before a line of Cossacks attempt to block their path to the airport and a standoff ensues, with Navalny supporters trying to form a protective ring around the opposition leader.
After an FBK supporter appears to elbow a man, a melee breaks out and several FBK members -- many of them wearing large backpacks -- are punched, kicked, and thrown to the ground.
Navalny wrote on Twitter that the attackers beat both men and women, and mocked police for failing to protect him and his team.
"You see how many police are usually at every airport? And here, especially in May, at the Anapa airport, two police officers for the entire airport," he wrote in one tweet.
Anapa police told TASS that no arrests had been made. The official state news agency also cited the leader of the Cossack Unit in Anapa, Valery Plotnikov, as saying that Cossacks were attempting to separate two conflicting groups when an FBK member was hit with milk, causing members of the foundation to retaliate.
Plotnikov claimed that members of Navalny's group beat two civilians, both of whom were taken to hospital, one with a broken nose.
One Cossack who participated in the action reportedly said that the original plan to hurl milk at Navalny and his supporters changed after an elderly Cossack was elbowed.
"The fight broke out because of that blow," Dmitry Slaboda told the Govorit Moskva radio station, according to Reuters. "We just wanted to show them that there is no room here for Navalny, who lives on American money."
Among his string of tweets pertaining to the incident, Navalny mocked suggestions that FBK members had initiated the violence.
"'Cossacks attacked the FBK'" -- that is just factually incorrect. The police and 'Cossacks' carried the attack out. The organizer (of the attack) is, of course, the state."
In other tweets he accused police of following him and his group during their stay in the Krasnodar region.
Artyom Torchinsky, a Navalny associate who is also a journalist for Dozhd TV, was taken to hospital with a head injury. Torchinsky told Dozhd TV from the hospital by phone that the assailants attacked the FBK members for no reason and shouted: "Get off of our land!"
FBK spokeswoman Kira Yarmysh wrote on Twitter that Navalny and some 30 members of his foundation traveled to Anapa to hold team-building exercises in the countryside outside the city located in Russia's southern Krasnodar region.
Navalny said earlier that local police in the region had detained him and his associates for several hours on May 13. Local authorities said that Navalny and his team were not detained, but just checked as part of a security campaign.
Cossacks, people of mixed Turkic and Slavic background, have longstanding ties to Russia's southern regions and were historically used as mercenaries by Russian tsars.
After being persecuted and banned across the Soviet Union, Cossacks have been allowed by Russian authorities to revive their traditions and have been used in a semiofficial capacity in their Krasnodar stronghold to enforce law and order.
Many Kremlin critics consider Cossacks' involvement in law enforcement illegal and say they are used as an instrument to crack down on dissent. In February 2014, Cossacks providing security for the Sochi Winter Olympics whipped members of the anti-Kremlin punk-performance collective Pussy Riot.
Kremlin spokesman Dmitry Peskov told journalists in Moscow on May 17 that he was unable to comment on the incident in Anapa.
"I would not like to make conclusions on something based on information from a single source," Peskov said.
With reporting by RFE/RL's Russian Service, tvrain.ru, and Interfax