A man suffered serious injuries including a collapsed lung when he was attacked by a large gang in Aberdeen city centre, police said.
The 55-year-old also underwent treatment for injuries including a fractured cheekbone following the assault in the Kincorth area on Saturday evening.
Grampian Police said the incident happened at about 2340 BST in Provost Watt Drive, near the Kincorth Shopping Arcade.
The man was passing the shops where a large group of people aged between about 17 and 30 had gathered.
He was beaten to the ground and then kicked on the head and body.
The man managed to get away and took a taxi to the home of a relative who called an ambulance to take him to Aberdeen Royal Infirmary.
Detective Chief Inspector Eric Leslie said: "This was a vicious and cowardly attack on a defenceless man who was seriously injured as a result.
"We are particularly anxious to trace the taxi driver who took him to his relative's address in the Great Western Road area of Aberdeen and we are also anxious to speak to the man who was with the victim just before the attack."
Mr Leslie said officers would be checking closed circuit television footage in the area and conducting house-to-house enquiries.