A mother has been charged with murder after an alleged stabbing that left one child dead and two other injured in the Blue Mountains.

The 42-year-old woman had told her husband she was taking their children on a picnic on Sunday but instead drove them to a quiet street in Valley Heights and allegedly attacked them with a knife about 1pm before turning it on herself.

The children — aged five, three and one — were strapped into their car seats when the alleged attack unfolded.

The five-year-old boy died inside the vehicle at the scene, while his two younger siblings suffered wounds to their necks.

The two children and their mother were treated by paramedics before being rushed to hospital in critical conditions.

The woman was charged with domestic violence-related murder and two counts of causing wounding or grievous bodily harm with intent to murder.

Police confirmed on Monday that the woman’s injuries were believed to be self-inflicted and identified her as the suspect in the alleged attack on the children.

7NEWS understands members of Sydney’s Kenyan community are rallying around the father, while the Kenyan consulate has confirmed it is providing assistance.

https://7news.com.au/news/crime/mother-charged-after-allegedly-stabbing-three-yo...