SYDNEY, Australia — At least 20 people, including pregnant women and children, have been killed in an ambush and retaliatory massacre by villagers in Papua New Guinea, according to news reports and a police spokesman in the South Pacific island nation.

The fighting began when six people were set upon and killed while returning from a ceremony on Saturday in the country’s central highlands, Teddy Augwi, the chief police inspector for Hela Province, told The Post-Courier, a newspaper in Papua New Guinea.

Relatives of the dead then retaliated, Inspector Augwi was quoted as saying.

There were conflicting accounts on the total number of victims, who were from rival communities.

A police spokesman, Dominic Kakas, told The New York Times that 16 women and children, including two pregnant women, were killed in the revenge attack.