Hundreds of people may have witnessed a double fatal stabbing in a city centre, police said.
Two men in their 30s were stabbed in the centre of Birmingham just before 6pm on Friday night. A 23-year-old man is being questioned about the incident.
West Midlands Police said one victim was understood to have been stabbed outside a Sainsbury's store on Martineau Place while the second was found slumped near Boots in Union Street.
Officers gave first aid to the men but both were pronounced dead at the scene.
A man was arrested in New Street near the Odeon Cinema minutes after the stabbings.
A police spokesman said: "It is believed there are potentially hundreds of people who may have seen the incident or the offender leave the scene following the incident and police are urging people to come forward as they may have vital information."
Inspector David Keen said: "Two men have suffered fatal injuries - these have been inflicted in the heart of the city at a busy time when workers and shoppers would be heading home.
"There are potentially hundreds of witnesses, either people who saw the stabbings or the offender leaving the scene, and I'd urge people to get in touch immediately - they could have vital information.
"A large police presence was quickly on the scene and a man was arrested swiftly."
The police spokesman said that Union Street had now reopened but small areas were still cordoned off in Union Passage, outside Sainsbury's in Martineau Place and near the Odeon Cinema in New Street while forensic investigations continue.