A 57-year-old man is in a critical condition in hospital after being attacked in Glasgow city centre.
Police said they were treating the incident on Hope Street, at Cowcaddens Road, at about 00:20 on Sunday as attempted murder.
The victim was taken to the city's royal infirmary but later transferred to the Queen Elizabeth University Hospital where he remains.
Police said they were studying CCTV for a description of the attacker.
'Were you out'
Det Insp Kevin Gilmour said: "A man has been left in a critical condition and it is vital that we find out who is responsible for his injuries.
"Officers are trying to establish a description of the suspect and have been speaking to those in the area and checking CCTV.
"However, we are appealing for anyone who has any information regarding the incident to come forward.
"Were you out in Glasgow last night? Or were you woken up during the night? If you remember anything that can help us, please come forward."