It comes after police were called to reports of a man being badly injured in the town centre's Lower Gardens park just before 1.30am on Saturday morning.

The teenager from Bournemouth, who has not been named, died at the scene.

His family and the coroner have been notified of his death.

The four men detained were all aged 18 and from coastal areas - two are from Portsmouth, one is from Poole and the other is from Bournemouth.

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Superintendent Gavin House of Dorset Police said: "Very sadly a young man has lost his life and our thoughts are with his family and friends.

"A full and detailed investigation is under way into this incident and I would urge anyone who saw what happened and has not yet spoken to officers to please contact us."

Mr House added that Bournemouth Square and a large area of the park had been cordoned off so the investigation could be carried out.

There will be an increased police presence in the area over the coming days, he said.