The suspected killer, named as 60-year-old Ljubisa Bogdanovic, shot dead six men, six women and a small child while they were sleeping, before shooting himself, Police Director Milorad VeljoviÄ‡ told Serbian radio and TV broadcaster B92.
The man's first victims were his son and mother, according to B92 and the RTS public broadcaster. Then the killer also shot his wife before turning his CZ-88 handgun on himself. Both Bogdanovic and his wife have been hospitalized and are in a serious condition.
All the victims were the shooter's relatives, who lived in five nearby houses, VeljoviÄ‡ said. The youngest victim was two years old.
The motive for the killings is unknown, VeljoviÄ‡ said, adding Bogdanovic was a veteran of the war in Croatia in the 1990s during the collapse of federal Yugoslavia.
"We have never seen a tragedy like this in Serbia, and for that reason a motive must be ascertained - what prompted this man to kill so many people in their sleep," he said.
Bogdanovic did not have a police record, VeljoviÄ‡ said.