At 11 a.m., police were called to reports of a car colliding with a pedestrian crossing the pedestrian crossing on the B334, Gosport Road near the junction with Marks Road.
The pedestrian, a 23-year-old man, was critically injured.
The car did not stay at the scene.
Officers want to hear from anyone who witnessed the incident or who may have captured the incident and the car involved on Dash Cam.
Anyone with information is asked to call police at 101 and reference 44220218456.
You can also contact the independent charity Crimestoppers completely anonymously at 0800 555 111 or through their anonymous online form at crimestoppers-uk.org.
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