The boy, named Adam by officers, was discovered near Tower Bridge in September 2001.

He is estimated to have been between four and seven years old and police have said the murder may have been part of a ritual ceremony.

Forensic evidence suggests the boy had strong links with a rural area in south-western Nigeria between Benin City and Ibadan, which is a 100 mile by 50 mile corridor.

Local mineral samples taken last year by scientists are said to match those found in Adam's body.

The body was without head or limbs

The London detectives, in co-operation with Nigerian police, will spend three weeks travelling to villages in the area.

They are hoping to find Adam's real identity and any clues which might lead to his killers.

Police believed the boy may have been subject to a West African-style "muti" ritual killing, commonly associated with southern Africa.

A �50,000 reward is already on offer for information leading to the conviction of his killers.

A second reward of �2,500, in local currency, is being offered for information leading to his identification.

Last year former South African president Nelson Mandela made an appeal for information which was translated into Yoruba, the local language, and posters went up in the area.

The case has had little coverage in the Nigerian media despite widespread press interest in the UK.