A family of seven, including four children, have been found dead with gunshot wounds at a rural property in south-west Australia.

The children died with their mother and grandparents. The three generations had moved to Osmington, a village of fewer than 700 people near the tourist town of Margaret River, in 2015 to grow fruit, media reported.

Police would not comment on the possibility of murder-suicide, but they are not looking for a suspect.

Officers were alerted by a phone call before dawn, Western Australia State Police Commissioner Chris Dawson said.

The bodies of two adults were found outside the house and the rest were inside. They all lived at the property, he said, adding it was a “horrific incident”.

“This devastating tragedy will no doubt have a lasting impact on the families concerned, and the local communities in our south-west,” Mr Dawson said.

Police were attempting to make contact with victims’ relatives, he added:

Philip Alpers, a Sydney University gun policy analyst, said the tragedy appeared to be the worst mass shooting in Australia since a lone gunman killed 35 in Tasmania state in 1996, prompting tough gun controls.

Australia’s gun laws are widely acclaimed as a success, with supporters including former US president Barack Obama.

A mass shooting – four deaths excluding the shooter in a single event – has happened only once in Australia since 1996. In 2014, a farmer shot his wife and three children before killing himself.

Farmers are allowed to own guns under Australian law because they have a need to use them to kill feral pests and predators or sick or injured livestock. But automatic and semi-automatic rifles and shotguns are banned from public ownership.

Samantha Lee, chairwoman of the Gun Control Australia lobby group, said: “Regional and rural areas are particularly vulnerable to these sorts of tragedies, because of the combination of isolation, sometimes mental or financial hardship and easy access to firearms. Australia has a history of higher rate of gun deaths in rural areas.”