Northumberland Road was shut along with a section of Victoria Road North, opposite Priory School, which was closed to cars travelling east while tape was used to stop pedestrians entering the area as they dealt with the incident just before 1pm.
The force has now confirmed they attended a ‘disturbance’ at an address on Victoria Road North before talking to a 45-year-old man leading to him moving to safety.
The man was then arrested and is in police custody.
An ambulance was also on standby at the scene.
A police spokesman said: ‘We were called to a disturbance at an address in Victoria Road North just before 1pm yesterday. Officers attended and a road closure was put in place while we negotiated with a man.
‘A 45-year-old man from Portsmouth has been arrested on suspicion of assault occasioning actual bodily harm. He remains in custody at this time.’
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A spokesman for South Central Ambulance Service said: ‘This was a police-led concern for welfare incident that we were on standby for but not required in the end.’