The video shows the naked man standing on snow-covered streets, being photographed by one police officer while several others looked on.
Another officer is seen grabbing the man by the back of the neck, forcing him to hold an ice scraper, then slapping him on the head and kicking him as he is directed into a police bus.
Welts are visible on the man’s back as he climbs into the bus.
The Interior Ministry, which oversees the riot police, issued an apology and said the episode was under investigation.
There were also signs of spreading unrest outside of Kiev, the capital.
In Lviv, the largest city in Western Ukraine, protesters occupied the regional administration building.
The region is a stronghold of support for European integration, the issue that set off the civil uprising in November, and home to many of the most aggressive protesters on the streets in Kiev.
Demonstrators similarly laid siege to the regional administration in Rivne, also in the West, where they demanded that riot police officers deployed to Kiev be sent home.
There were parallel actions in a number of other cities, including in Cherkasy in central Ukraine, where several thousand demonstrators briefly clashed with the police who protected the administration building and at one point fired several shots in the air, the local news media reported.
The protests, while not clearly coordinated, were all in response to the increasingly ominous situation in Kiev, where demonstrators near the Dynamo soccer stadium had clashed fiercely with the police throughout this week, burning police buses, beating some officers, and setting large numbers of tires on fire.
Among the most chilling developments were reports of demonstrators being kidnapped — in some cases at hospitals — or detained by the police and taken to undisclosed locations.
Ihor Lutsenko, a civic activist and leading organizer of the opposition movement who has been a strong advocate of peaceful protest, was grabbed early Tuesday morning at a hospital where he had brought another demonstrator injured by a stun grenade during clashes with the police.
The second man, Yuriy Verbytsky, was later found dead on the outskirts of Kiev.
Another body was found in the same area and also showed signs of abuse, Ukrainian news media reported.
In an interview from his hospital bed on Thursday, Mr. Lutsenko described being forced into a van by men whom he described as “very professional” and taken to a forest where he and Mr. Verbytsky were beaten and interrogated, but mostly kept apart.
Mr. Lutsenko, who was beaten severely at times on the head with wooden boards, had a tooth knocked out and his left eye was blackened.
There were bruises and cuts all over him.
He said that at one point he was forced to kneel in the woods in front of a tree, a plastic bag was put over his head and he was told to pray.
He said he was certain he would be killed.
Instead, his captors left, and he trekked injured through snowy woods until he found a local resident who helped him.
Mr. Lutsenko said that his captors appeared to be former police officers based on the way they questioned him and repeatedly verified information that he supplied, and made clear they were aware of the cars and motorcycle registered in his name.
He said that he was held in a sort of shed in the woods, and that once his interrogators confirmed his leadership role, they demanded information about the opposition’s plans — an absurd question given the chaotic and unpredictable nature of street protests over the last few days.
“They were kind of sadists,” Mr. Lutsenko said, “really brutal.”
Mr. Lutsenko said he did not know Mr. Verbytsky before being asked to drive him to the hospital to treat an eye injury, but that he believed he may have received harsher treatment because he was from Lviv, in Western Ukraine, home to many of the most aggressive protesters in the opposition.
Ukrainian news media on Thursday reported yet another disappearance.
Dmitry Bulatov, the head of a motorist protest group called AutoMaidan, was apparently detained along with other members of his group, which leads caravans of vehicles in demonstrations against the government.
After continued clashes overnight, protesters battling the police in the Ukrainian capital agreed to the temporary cease-fire on Thursday morning as opposition leaders planned to attend a second round of negotiations with Mr. Yanukovich.
The talks, scheduled for the afternoon, were repeatedly pushed back.
Late on Thursday, two of the opposition leaders emerged from the meeting with Mr. Yanukovich to urge a continuation of the truce.
They said they had achieved a tentative agreement that would set free dozens of detained protesters and potentially create another occupied space similar to Independence Square, where demonstrators have camped out since early December.
They also said that a package of legislation broadly suppressing political dissent that was rammed through Parliament last week by Mr. Yanukovich’s supporters would be revisited at a special legislative session next week.
There were howls of dismay among some of the protesters gathered to listen to the two leaders, the former boxing champion, Vitali Klitschko, who leads a party called the Ukrainian Democratic Alliance for Reform and Oleg Tyagnibok, the head of the nationalist Svoboda Party.
Mr. Klitschko and Mr. Tyagnibok said the authorities had also given guarantees that the police would not fire on protesters with live ammunition, something that officials have denied ever occurred, even as four demonstrators were shot to death during clashes with the police early Wednesday.
The opposition leaders, who head the three largest minority factions in Parliament, have struggled in recent days to command the respect and support of the demonstrators on the street.
They were jeered and booed at a rally on Sunday to protest the new legislation.
Despite the urging of a continued cease-fire, it did not appear that Mr. Yanukovich had given any major ground.
The opposition leaders had been demanding early presidential elections — sooner than the regular vote scheduled to take place in March 2015 — or the dismissal of some or all of the appointed government ministers.
Although the General Prosecutor’s office confirmed that two men had been shot to death during battles with the police, a coordinator of medical services for the opposition has put the death toll at five.
As the standoff continued, international consternation appeared to be mounting and there were renewed calls, including by the United States, for a peaceful resolution to the crisis.
The European Union said that its foreign policy chief, Catherine Ashton, would visit Kiev next week.
Source: The New York Times