Desdemona Lioce had been on the run since 1995
An Italian policeman has been killed and another injured during a shoot-out on a train involving suspected members of a violent guerrilla group that succeeded the infamous Red Brigades.
One suspected militant, Mario Galesi, also died and his companion Desdemona Lioce was arrested.
The incident took place on a Rome-Florence train.
Lioce, who has been on the run since 1995, has been linked to the murder of Massimo D'Antona, a government labour adviser shot dead in 1999.
Sunday morning's incident reportedly started when an officer asked a couple for identity documents in a routine check, and the man allegedly pulled out a pistol.
"The passenger put a gun to the head of one of the policemen and fired," a witness said in an interview with state radio.
"Then he fired several more shots [at the other officer]," the traveller said.
The injured policeman suffered a serious lung wound.
A third policeman rushed to the aid of his colleagues, firing several shots, one of which fatally injured the gun-wielding passenger.
Heirs of terrorists
Lioce, 43, and 37-year-old Galesi are suspected of belonging to the New Red Brigades, heirs of the left wing group that sowed violence and terror in the country through the 1970s and early 1980s.
After Mr D'Antona's slaying, another labour expert, Professor Marco Biagi, was killed outside his home in Bologna in 2001.
The Red Brigades' logo was scratched onto the door of a house next to the spot where Biagi was gunned down.
The Red Brigades logo was found near the scene of Biagi's murder
Italy's Interior Minister Giuseppe Pisanu said that he hoped the arrest would shed light on the two earlier murders.
"We are getting close to the moment when we can do justice to the memory of Professor Biagi and Professor D'Antona," the Ansa news agency quoted Pisanu as saying.
The New Red Brigades claimed responsibility for the killings of D'Antona and Biagi and the same gun was used in both attacks.
The original Red Brigades reached the peak of their notoriety in 1978 when they kidnapped and killed former Italian Prime Minister Aldo Moro.