A one-year-old girl and a three-year-old boy have been stabbed to death at a home.
Police were called to reports of a man and two children injured in Aldborough Road North in Ilford, east London, at about 17:30 BST on Sunday.
The girl was pronounced dead at the scene, while the boy died in hospital, the Met Police said.
A 40-year-old man was also taken to hospital with knife wounds. Police said all three were all known to each other.
The Met has launched a murder investigation, but the force said it was not looking for anyone else in connection with the deaths.
Jas Athwal, the leader of Redbridge Council, tweeted: “Earlier today there was an incident in Ilford. Two young children have passed away & an investigation is ongoing.
“My thoughts are with the family and wider community who are grieving this unspeakable tragedy.”
There have been 21 fatal stabbings in London so far this year – six of them are known to have happened in the borough of Redbridge.
On 20 January three men – aged 29, 30 and 37 – were stabbed to death on Elmstead Road in Seven Kings and 24-year-old Ricardo Fuller was also fatally stabbed outside a nightclub near Ilford High Road on 7 March.