The father of a taxi driver who was fatally stabbed in Melbourne has appealed for public help after two witnesses helped police produce an image of the suspect.

Somali refugee Mohamud Muketar, 31, was repeatedly stabbed in what police described as a "savage and brutal attack" in the inner northern suburb of Fitzroy in April last year.

The man has been described as having a lanky build and shoulder-length sandy blond hair. ( Supplied: Victoria Police )

Mr Muketar's father, Muktar Hussan, said he feared the killer could strike again, given the random nature of the attack on his son.

The victim parked his taxi near the Fitzroy police station about 11:30pm and was walking home when a man confronted him near the corner of Condell and Napier streets.

Police said Mr Muketar and the killer spoke for about 20 seconds before he was stabbed multiple times and left dying on the ground.

The killer ran past a man and a woman in a nearby reserve. They described him as being Caucasian, aged between 20 and 40 years old with a lanky build and shoulder-length sandy blond hair.

Seconds after the murder, a cyclist rode through the area and passed the taxi driver as he lay dying in Napier Street.

Detective Senior Sergeant Stephen McIntyre said the cyclist may have seen or heard the murder, but has yet to come forward despite an earlier appeal for information.

He said Mr Muketar had a small amount of money on him but it appeared nothing was stolen.

"We've looked into his family history, his personal and social life. There is nothing that explains why he might be targeted.

"He was savagely attacked, it was a brutal attack and it was sustained for a period of time."

The killer was last seen running along Wood Street.

A white Toyota Yaris was seen in the area about 10 minutes after the stabbing. ( Supplied: Victoria Police )

Detectives also want to speak with the driver of a white Toyota Yaris seen travelling around the area about 10 minutes after the crime.

The car stopped twice in an alleyway behind the Napier Hotel; the first time for three minutes and the second for about a minute-and-a-half.

"We don't know whether that car contained someone that picked him [the suspected killer] up, or whether he himself may have been in that car driving it," Detective Senior Sergeant McIntyre said.

Police have so far received about 80 phone calls from the public but Detective Senior Sergeant McIntyre said more information was needed to solve the case.

"We don't know whether we have spoken to the offender, but if we have we haven't got enough evidence to link them to the crime."

Sorry, this video has expired Police have released CCTV of a cyclist who may have witnessed the fatal attack

'Who killed my son?'

Mr Hussan lived with his son and was sleeping at the time of the murder.

He had driven the same taxi during the day and initially did not think anything was wrong when he could not find the car key in the morning, because his son would sometimes be with a friend.

"I never thought [there was] any problem," Mr Hussan said.

As he approached the taxi he noticed that the area had been cordoned off.

"The whole area is closed, still I don't have any clue, I don't have any problem."

Later police told him of his son's death.

He said his only question was: "Who killed my son?"

"My son was not involved in any problem, he [didn't] have a drugs-related [problem], he [didn't] have a woman problem because he [was] working weekends."

He said the family moved to Australia from Somalia in 1998 for a better life and opportunities.

Mr Hussan fears someone else could be killed next.

"The criminals are inside society so it can happen to any of you, or anyone in the community tomorrow."