Man dies in police custody after being arrested for fighting with teenager in Adelaide

A man has died in police custody after he was arrested for fighting with a teenager in Adelaide.

South Australian Police have confirmed the incident will now be investigated to determine whether the officers involved in the arrest acted appropriately.

Police responded to a number of calls from the public about two men, respectively aged 41 and 17, fighting on King William Road, Adelaide, near Parliament House around 9.30pm last night.

"We're aware a fight occurred for over five minutes in the location," Detective Inspector Brett Featherby said.

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"It's evident the fight has spilled onto the roadway and as a result traffic has stopped."

Officers arrived while the men were still fighting and they were both restrained and arrested.

However, during the arrest the 41-year-old man became unresponsive.

Paramedics and police started CPR but the man died at the scene.

Police have determined the incident as a death in police custody.

Featherby said the actions of SA Police officers will be examined to ensure they acted "in accordance with policy, process and legislation".

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The 17-year-old was taken to hospital due to injuries from the fight and was later unarrested by police, Featherby said.

Major Crime and Ethical and Professional Standards detectives are investigating the incident.

The incident will undergo a criminal and coronial investigation.

"Last night's incident is not related to recent gang activity in the city," Featherby said.