In fact, the oldest genetically identifiable family "were definitely murdered, there are big holes in their heads, fingers and wrists are broken," Alistair Pike from Bristol University told the BBC.

The researchers, whose report was published in the PNAS scientific journal, said comparisons of DNA extracted from bones found in one grave confirmed it entombed a mother, father and their two children. The son and daughter were buried in the arms of their parents.

"We're really sure, based on hard biological facts not just supposing or assuming," said Wolfgang Haak of The Australian Center for Ancient DNA in Adelaide, conducted the DNA analysis.

The four graves held 13 bodies, eight children and five adults. In two graves, DNA was preserved enough to allow comparisons among the occupants, researchers said.

One of the graves contained the nuclear family, while the other grave contained three related children and an unrelated woman, the British broadcaster said.