A man has been left with facial injuries after two people on a moped threw an unknown liquid at him in London's Knightsbridge.
The Met Police said the 47-year-old man was attacked in Walton Place at about 20:30 BST by "two males" on a moped.
The force said the man had been taken to a central London hospital but has since been discharged.
A spokesperson said it was not yet known if the liquid thrown was a corrosive substance.
They said no-one had yet been arrested but officers remained at the scene and inquiries were ongoing.
The incident follows a recent rise in the number of attacks involving corrosive substances.
More than 400 were carried out in the six months up to April 2017, according to figures from 39 forces in England and Wales.
The Metropolitan Police has said its response cars will now carry equipment that will help officers to better deal with calls to such attacks.
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