The suspect, Donato Bilancia, was described as a compulsive gambler with a long criminal record, and "in a precarious psychological state". He was found in possession of a .38 revolver matching the one used in the murders, and of a dark Mercedes of the kind described to investigators by a transvestite prostitute who narrowly escaped death at the hands of a middle-aged man on 24 March.
Police declined to say whether Bilancia was implicated in the murders of two women in train lavatories in Liguria in mid-April.
"Bilancia is one of the people we have begun to suspect most strongly over the past few days," said Genoa's chief prosecutor, Vincenzo Scolastico, after the arrest.
"We have had him under close surveillance."
The string of murders began on 9 March when the naked, disfigured body of Albanian prostitute Stela Truya, 25, was found on a cliff, half a kilometre from the home of Bilancia's parents in Cogoleto, near Genoa. On 18 March, Ukrainian Sljudmyla Zuskova, 23, was forced to kneel in a quiet lane near Pietra Ligure, where she was shot in the back of the head.
This pattern was to be repeated in the killings of the Nigerian Evelin Esohe Edhogaye, 27, on 29 March in Cogoleto, and of Albanian Mema Valbona, 21, on 13 April in Pietra Ligure.
The transvestite Julio Castro, known as Lorena, was accosted in a dark lane near Novi Ligure on March 24, by a man in a Mercedes who pulled a gun on him. Lorena was saved by two passing security guards who noticed the struggle and pulled over to help. The guards, Candido Rando and Massimino Gualillo, were killed. Lorena was wounded and left for dead.
Bilancia began building up his police record as a child. He spent time in prison for theft in 1973, 1981 and 1983. In 1990 he was arrested after threatening a prostitute with a gun.
Police in the resort towns along the Ligurian Riviera are now seeking to establish whether Bilancia was present in any of the local casinos on the night of 18 April, when the body of Maria Angela Rubino was found in the lavatory of the Genoa- Ventimiglia express train with a bullet in the back of her head.