The alleged assailant gunned down five men and four women after a drinking session on Saturday night turned violent in the village of Redkino, some 110 kilometres (70 miles) northwest of Moscow, the Investigative Committee said.
"During the get-together there was a domestic dispute between the guests, after which the suspect left and then returned with a hunting rifle," investigators said in a statement, adding that the man had been "drinking spirits".
"He fired several shots, as a result of which at least nine people died," investigators said, raising the death toll by one from figures given earlier Sunday morning.
Investigators said the shooter -- a 45-year-old resident of Moscow -- was detained on suspicion of mass murder after survivors managed to call the police.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)