It is understood that the driver of a grey-coloured Vauxhall Astra allegedly tried to run over a man walking along Bristol Road South near the junction with Belton [Grove], at about 1.30pm.
The car is then believed to have stopped on the kerb and the pedestrian has reached inside the car through a rear window and stabbed one of the occupants, however no one has reported being stabbing.
Both the car and the pedestrian have then left the scene.
The man is described as white, aged in his late teens or early 20s and was wearing a white mask or scarf and black trousers or tracksuit bottoms.
Police investigations are continuing with officers trawling CCTV footage and carrying out house-to-house enquiries in the area – but anyone who may have seen the incident is urged to contact them.
Det Sgt Karen Taylor from Force CID, said: “This appears to have been a serious offence involving a weapon which we believe to have been a knife.
“We’d urge anyone injured during this incident to contact us so we can make sure they are okay.
“It occurred in broad daylight on a busy city centre route so we asking anyone who witnessed the incident or may have captured it on their dashcam to get in touch.”
Anyone with information can get in contact via Live Chat at www.west-midlands.police.uk between 8am and midnight or call 101 any time – quoting log 2061 of 9 June. Alternatively to remain anonymous call Crimestoppers on 0800 555 111.
How do they know it was a stabbing if noone reported it? Wearing black trousers or tracksuit bottoms and a mask or scarf? Pretty crap discription thats half of the youngsters around here that dress like that.