A mother and her two daughters aged six and eight have been found dead in a septic tank in a suspected murder-suicide.

The trio were found in the sewage tank after the children's father reported them missing on Sunday at 10:18pm in the small town of Helenów Pierwszy, Konin County, in west-central Poland.

He told emergency services there were 'disturbing' signs that they had fallen into the septic tank.

A rescue operation was launched with four fire units and a diving team but before they arrived a woman and one child had already been pulled out by two men, with the other child remaining in the tank.

The mother, 32, was pronounced dead at the scene, while the children were rushed to hospital where they died.