Police were called to Dunsmore Close, Southsea yesterday morning after reports of a robbery at around 6.20am.
The taxi driver has been left with serious injuries to his face after the unknown men approached his car and asked him a question.
The suspects, described as white and in their 20s, reportedly ran off towards Portsmouth & Southsea railway station.
Anyone with information regarding the incident should call police on 101, quoting 44160418149.