Police are appealing for witnesses after a 43-year-old man was assaulted by four men yesterday morning.
The victim sustained serious head injuries requiring hospital treatment after the attack at around 1.15am in Railway View, Landport.
A 25-year-old man from Southsea and a 27-year-old man Waterlooville were arrested in connection with the incident.
Both have been released from custody but remain under investigation.
Police believe the group left the scene on foot following the incident in the direction of the footbridge to Greetham Street.
They have been described as white, aged in their mid-20s and two of them were wearing white tops.
Officers would like to hear from anyone who witnessed the incident or has any information that could help identity those responsible.
Anyone with any information is asked to call police on 101, quoting 44170240203.