Four teens allegedly responsible for a series of violent crimes – including bashing a man so badly he may have life-long serious injuries - have been arrested and charged in Melbourne's west.

Police moved on the group in a series of raids in the western suburbs on Monday morning and arrested three 16-year-olds and a 15-year-old.

Police allege the teens bashed a man in Rochester Street, Braybrook about 7.30pm on Wednesday, March 13 and left him for dead.

The man, 45, was found by emergency services and taken to hospital, where he still remains with serious injuries that may stay with him forever.

Police allege that only minutes earlier the group had tried to steal a phone from a man on Beachley Street. Police have not made it clear if it was the same victim.