A man has been arrested after four women were stabbed in west London, police said.
The attack took place in Hampton at around 10.35am on Friday near a branch of supermarket Sainsbury's.
All four victims suffered knife wounds and one was reportedly airlifted to hospital, where her condition was described as life-threatening
A Metropolitan Police spokesman said a man in his 60s was arrested at the scene on suspicion of attempted murder.
The Met said police were called at around 10.35am to The Avenue in Hampton after reports of a man in possession of a knife.
The spokesman said: "Officers attended and discovered three women suffering from knife wounds.
"The London Ambulance Service also attended and are providing treatment to the women.
"Their conditions are not thought to be life-threatening or changing at this time.
"A fourth woman who had also suffered knife wounds was subsequently located at a nearby property.
"She has been taken to hospital where her condition at this stage is thought to be life-threatening."
The spokesman added: "At this early stage, the incident is not believed to be terror-related."
A member of staff at the nearby Hampton Pub said the knife man was only targeting women in the unprovoked attack.
The woman, who did not want to be named, added: "It's so awful - four women have been stabbed in the car park. He only went for the women.
"The man ran through and started attacking them. It didn't seem like they knew him it was completely unprovoked.
"One lady is in very bad condition, she had to be air-ambulanced out.
"If it had been 10 or 20 minutes earlier there would have been children there because it's right outside a primary school.
"He was caught very quickly just outside the car park.
"He appeared to be out of it, on drugs or crazy. He must have been very angry to go out and unprovokedly stab those women.
"The woman who was badly stabbing in the back made it up to the police station and raised the alarm.
"She is well-known locally and always goes shopping there all the time."
A member of staff at Tangley Park Children's Centre, which backs onto the scene of the stabbing, said: "We kept all the children safe and kept them in the building until we knew it was safe.
"It's just such a shock - our parents and children could have been walking to their cars at that time.
"Our sympathies go out to everyone who was hurt and we are really glad none of our families were involved."