Photos taken of the scene show police and at least one ambulance attending the scene along the A3 leading to London Road at 6.50pm on Saturday.
A witness reports seeing two police cars and an air ambulance also in attendance, with one lane of the two lane approach into Hilsea being closed.
Reports on social media suggest that the incident involves a motorbike and several cars.
Hampshire Constabulary and South Central Ambulance Service have been contacted for further information.
A Scas spokeswoman said: ‘We were called at 6.45pm to the A27 to an incident involving a motorbike.
‘We sent to the scene one ambulance crew who were assessing and treating one patient who, following treatment at the scene, was taken to the Queen Alexandra Hospital