Police arrested the gang of four men in streets near to the scene of the stabbing just after 4am on Sunday.
The 32-year-old victim was rushed to Västerås hospital with serious stab wounds in the early hours of Sunday.
The hospital confirmed to police that the man had died from his wounds at 6.08am on Sunday.
Police confirm that significant uncertainty remains around the nature and motives of the murder on Sunday morning. Two of the suspects were reported to have themselves sustained injuries in the attack.
“One was injured in the hand and one in the foot. It could be a question of a tumult outside a party,” said Anders Helin at Västmanland police to local newspaper VLT.
The murder weapon had not yet been recovered by Sunday morning.
The four suspects, who are aged between 18 and 20-years-old, will be interrogated during Sunday.
The murder occurred in Bäckby, a residential area in the western suburbs of Västerås.