Stones and Molotov cocktails were hurled at police.
The Ukrainian Interior Ministry said in a special statement that "despite prolonged negotiations between the opposition and the authorities, as well as preliminary truce agreements, some radical forces beyond the protest leaders' control have resumed attempts to provoke police into using force."
Police and protesters stayed in place on either side of the barricades. Heavy smoke from burning tyres enveloped the area. Sporadic explosions of noise grenades and firecrackers were heard. Demonstrators armed with sticks kept banging empty barrels.
In the middle of the night the Interior Ministry said the body of a police with a bullet wound in the head had been found in one of the city's neighborhoods. It was spotted by security personnel guarding a construction site nearby.
Witnesses said they had seen two unidentified persons running away from the scene of the attack. The police were called.
The dead man was identified as a 27-year-old sergeant from the local police office. He was on his way from work to a hostel of the Berkut crack police unit. The man was unarmed.
Also, law enforcers said on Friday three police had been seized by rioters near Independence Square, where a mass opposition rally was in progress.
The Ukrainian Interior Ministry said the rally's vigilantes attacked three police who were on duty at the moment. One suffered a knife wound.
The police were reportedly kept for a while in the building of Kiev's city administration, earlier seized by opposition protesters.
The wounded police has now been freed and taken to hospital. The two others are unaccounted for.
Shortly before that the Ukrainian Interior Ministry warned Radical Party leader Oleg Lyashko, a member of the national parliament, he might be indicted on criminal charges for uttering public threats against law enforcement officials.
The protesters show no intention of leaving the building of the Agricultural Policies and Food Ministry in Independence Square. An opposition activist who introduced himself as the building's "governor" said that the rooms could accommodate about 3,000 people for the night.
"We shall be giving them something to eat and making tea for them. Here they will be able to get warm," he said.
Dozens of people spent the night on the floor in the ministry's corridors. Most of the offices are locked and sealed. On Friday, the staff were allowed to take out their personal belongings.
The ministry's press-service said that the demonstrators had seized the building by force, smashed doors, windows and CCTV cameras, control panels and electric switches. The security personnel who tried to offer resistance were beaten up.
Agriculture Minister Nikolai Prisyazhnyuk said on Friday that the seizure of the ministry's building might cause great harm to the country's agriculture.
"Losses for farming may be critical. This will deal a blow on social benefits. The farming sector has become the economy's growth engine. The disruption of its normal operation would hit the socially vulnerable groups of the population in the first place.
TASS