The security camera photograph shows a man walking behind Emanuel Spiteri, the last of the murderer's five victims, as they walked through Charing Cross station in central London hours before he died.
Detectives also appealed for a woman wearing jeans and a white top, who passed the two men as they walked through the station, to come forward.
A police spokeswoman said: 'We are pleased with the quick response and every phone call is being investigated.'
The picture was taken from a security video film at the station at 10.32pm on 12 June and shows the suspect emerging through a doorway behind Mr Spiteri.
In a letter published in the Evening Standard yesterday, Dennis Nilsen, the mass murderer, said the release of a photofit of the suspected killer would provoke the man to murder again if he is not caught. He said the killer would feel an 'irresistible urge' to carry on.