Unidentified attackers armed with knives killed 12 people, including three children and a newborn, who had gathered Friday for a celebration at a home in a Krasnodar region village, authorities said. The attackers then tried to burn the bodies.
The motive for the brazen killings in Kushchyovskaya, a farming village of about 100 homes, was unclear. Prosecutors from Moscow have been sent to help investigate.
Prosecutors said one of the children was strangled and another died of smoke inhalation. The other two children and all eight adults died of stab wounds, with some of them stabbed as many as 10 times.
Two families were visiting the host family, a farmer and his wife, Krasnodar emergency services spokesman Alexander Tabakov said.
"The three families were going to celebrate some holiday because there was a lot of food and drinks on the table," he said.
Tabakov said the killers tried to hide the crime by moving the bodies to the second floor of the house and then setting the house on fire. The bodies were doused with kerosene, with a trail of kerosene leading downstairs, but a fire set on the first floor fizzled out before reaching the second floor.
Nothing was stolen from the house, he said.