Police hunting the killers of black Merseyside teenager Anthony Walker have arrested two more men.
Merseyside Police said on Monday that they also wanted to question Michael Barton, aged 18, and Paul Taylor, 20, from Huyton.
Mr Walker, 18, was attacked with an axe by a gang of white men in what police said was a racially-motivated incident.
A 17-year-old is already being held, while a fourth man, aged 18, arrested on Sunday, has been released on bail.
'Will not rest'
Mr Barton and Mr Taylor may have left the UK, police said.
The two men arrested on Monday evening are aged 26 and 29.
Det Ch Supt Peter Currie, of Merseyside Police, said Friday's attack in McGoldrick Park, Huyton, was "despicable and abhorrent".
He said he was very pleased with the public response, with the force having received more than 50 calls about the murder.
Mr Currie added: "I would urge anyone else who has information but hasn't yet made that call, please pick up the phone and tell us what you know.
"I would like to reassure the community that we will not rest until those responsible for taking Anthony Walker's life are brought before the courts."
Floral tributes have been left at the scene of the attack
Mr Walker was beaten up weeks earlier, but his family did not report it as he was with a white friend at the time and they did not consider it racially motivated, Merseyside Police said.
Comparisons between the attack and the murder of Stephen Lawrence were dismissed.
Local MP Edward O'Hara, the Labour MP for Knowsley South, said there were important differences between Mr Walker's killing and the murder of Mr Lawrence in Eltham, south-east London in 1993.
He said: "There is a certain surface comparison but this act was random, exceptional and representative of absolutely nothing."
Mr O'Hara said it was a racist attack but "entirely untypical of the community in which it happened".
'Talk to them'
Mr Walker's mother Gee has said her son was killed "purely because of the colour of his skin".
The dead man's sister Dominique, 20, appealed for people to help catch the gang who attacked her brother on Friday night.
"If anybody knows anything, they have got to talk to the police," she said.
"Talk to them because we need the information. I need to find out who did this to my brother."
Mr Walker had spent the evening with his white girlfriend before the attack.
Book of condolence
As they waited for a bus outside the Huyton Park pub with his 17-year-old cousin they were subjected to a "torrent of racial abuse" by a man in his 20s wearing a hooded top.
They did not retaliate and left to find another bus stop, but were followed and, as they walked through a park, were attacked by a gang of up to four men.
Mr Walker's girlfriend and cousin ran to get help. When they returned Anthony was slumped on the ground with massive head injuries.
An axe was found embedded in his skull.
A book of condolence was due to be opened at Mr Walker's local church, the Grace Family Church, in Aigburth, on Tuesday.