WARNING - DISTRESSING CONTENT: Horrifying video has revealed the moment a young boy accidentally hanged himself as he played in his backyard before his sister bravely stepped in to save his life.

The three-year-old boy was playing at his Dongfang home on the Chinese island of Hainan on Friday when he stood on a barrel and tied a rope to the gate of the driveway.

In the distressing clip, the boy can be seen with the rope around his neck before the barrel suddenly rolls away, leaving him dangling from the gate.

He frantically kicks his legs trying to free himself as his younger sibling watches on.

Hanging for more than a minute, he is saved by his six-year-old sister who rushes to his aid and lifts him up before he falls to the ground.

His mother, who was cooking at the time, rushes out after cries for help from his sister before she picks him up and takes him inside.

The boy was rushed to hospital in a critical condition after falling into a coma, The Paper reported. His condition has since improved.

The video quickly went viral on Chinese Twitter-like site Weibo and has been viewed more than 290 million times.​

Users praised the boy’s sister for her quick thinking.

“His sister is great, she saved his life,” one person wrote.

Others also spotted the youngest child was attempting to roll the barrel back to his brother to enable him to stand on top of it.

The mother has since said she will pay more attention to her children.