A man in his 30s has been taken to hospital with life-threatening head injuries after an attack in Brighton's gay quarter.
The victim was assaulted in the very early hours of this morning (26 October) in the area around St James's Street and was admitted to Royal Sussex County Hospital.
A scene guard from Sussex Police remains in the area while officers carry out forensic examinations and speak to locals.
Detective Inspector Miles Ockwell from Brighton and Hove CID said: 'We are in the early stages of the investigation and would appeal to anyone who has not yet spoken to officers to please come forward.'
He added: 'We believe the suspects may have fled the scene of the attack on a motorcycle.'
Police are urgently appealing to anyone who might have seen or heard any suspicious activity between 11.30pm last night (25 October) and 12.30am today in the area of St James's Street, the New Stein or Lower Rock Gardens.
If you have information, call 101 quoting Operation Redshank. You can also leave an anonymous message with the independent charity Crimestoppers on +44 (0)800 555 111.