No one was injured in the incident, although two elderly women needed treatment for shock, after the homemade bomb went off in a black plastic bag at about noon.
Once again the Sainsbury supermarket chain appeared to be the target of the attack, with the device left close to a store in Eltham high street.
Anti-terrorist officers and forensic experts cordoned off the area and searched for clues to the person behind the extortion and terror campaign who has alluded capture for more than four years.
The device was placed at the base of a metal street map close to a bus stop at the entrance to a small shopping mall leading to the Sainsbury's supermarket.
A Scotland Yard spokesman said: "We suspect this to be down to the person or persons calling themselves the Mardi Gra bomber."
Detectives warned earlier this month that the bomber could kill soon.
A 17-year-old man was injured in the leg just over a week ago when a shotgun device exploded outside a Sainsbury's store in Forest Hill, close to Eltham.
The bomber turned his attention to Sainsbury's in November 1996 after originally pursuing an extortion campaign against Barclays Bank from 1994.Reuse content