The arrest came after a breakthrough when police discovered some of Akhlaq's clothing in a stream close to where he was killed in a crowded park on Sunday.
Forensic scientists were last night examining the clothing, recovered by teams of police searchers on the banks of a stream 100 yards from where the boy's body was found in Salt Hill Park, Slough, Berkshire.
The man leading the hunt for the killer, Detective Superintendent Michael Short of Thames Valley Police, said after the find: 'This could be a highly significant step for us. It was vital for us to find these clothes.'
Akhlaq, who had been in the park while his father and uncle watched cricket, had been beaten, strangled and dumped naked in undergrowth.
The items recovered, a jumper, jeans, black trainers and one sock, were all identified by the boy's family; the jumper recovered was not the same as the one police had originally been told he was wearing, but the family said they had been mistaken. However, still missing are the boy's white shirt, the other sock and his underwear.
Thames Valley officers said last night that they would be liaising with Lancashire detectives over the unsolved murder of Imran Vohra, aged nine, who was found strangled and sexually assaulted in undergrowth near a park in Preston, Lancashire, in July 1985. He had disappeared on his way home from school. However, police said there were differences between the cases.
A spokesman also disclosed that other forces had been in contact, but declined to give details.
Detectives, who have warned parents in the area to be on their guard, said that more than 150 people had come forward with information. Police are anxious to interview everyone who was in the park on Sunday afternoon and also want to see photographs or video films taken at the time.
The park remained sealed off yesterday as police continued their search, with bunches of flowers laid at the main entrance.
At Akhlaq's home nearby, his mother, Nasia Razzaq, 31, who was being comforted by women from the Asian community, called for the death penalty for her son's killer.
Speaking through an interpreter, she said: 'The whole family supports myself and my husband when we say the man who killed my son should die. It is not just vengeance - it is what is right. In my home country the person who took my son's life would pay with his own life, it is no more than he deserves.
'Britain is supposed to be civilised and yet men who kill children . . . do not have to pay the ultimate price - that can't be right.
'If such a killer had been caught in my country of Pakistan I would have been able to see him properly punished.'