A man and woman were attacked by a group of six men in Chesterfield town centre.
Detectives investigating the attack on the couple - a man aged 26 and a woman, 22 - want to hear from witnesses to the incident, including a taxi driver who shouted at the attackers to stop.
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A Derbyshire Police spokesman said: "At around 4.30am on Sunday, May 13, we believe a 26-year-old man and a 22-year-old woman were attacked by six men on Holywell Street,
"The man is thought to have been dragged into the road where he was punched and kicked multiple times on the floor.
"He received hospital treatment for injuries to his face, head, shoulder, legs and back."
He added: "We would particularly like to hear a the taxi driver who we believed shouted at the men to stop but has not since come forward to us."
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Call DC Angie Dawson at Derbyshire Police on 101, quoting reference 18000217647.
Crimestoppers can also be contacted on 0800 555 111.