A man suffered nasty burns after a noxious liquid was sprayed into his face.
The 41-year-old was walking along a bridle path in Oldham when he was approached by two youths.
As he agreed to light a cigarette following a request from one of them, the other sprayed a liquid into his face.
The liquid burned the man's skin and he fell to the ground.
Police have appealed to the public to help catch the two men. One is said to be a Asian, about 16, 5ft 4in tall and skinny. He has short black hair, shaved lines in his left eyebrow and a thin line of hair along his jawline. He was wearing a black tracksuit top with a red stripe down the arms, charcoal coloured jeans and had a local accent.
The other is also Asian man, about 17, 5ft 7in tall and skinny. He has black hair, thick bushy eyebrows and a hooked nose. He was wearing a brown scarf, a black zip-up tracksuit top with a silver badge and black jeans.
Detective Constable Andrew Swettenham said: "It is not yet known what the substance was but it began burning his skin immediately. Fortunately he wasn't badly injured but we are treating this attack seriously.