Shootings raise fear serial killer is at large.

Fears grew Friday that a serial killer was stalking low-income housing projects in the suburbs of Paris, where the same weapon has been used to murder four apparently innocent citizens since November.

The latest killing on Thursday of a 47-year-old mother, shot dead near her home in the Essonne suburb, prompted Interior Minister Claude Gueant to vow every effort was being made to find the killer.

All the victims were shot with the same small-calibre 7.65-mm weapon by a gunman who fled on a motorbike, recalling the methods of an Islamist extremist killed by police in southern France in March after murdering seven people.

While nothing suggests any political or religious motives in the shootings, police are probing any possible links with several other homicides in a 10-kilometre radius of the southern outer suburbs.

"That is a concern, but in any case, as in every criminal inquiry, we are putting every effort into finding out who is behind this," Gueant said.

Local prosecutor Marie-Suzanne Le Queau told journalists the first killing was different from the others, although carried out with the same gun.

"The way of killing is not identical in the four cases," Le Queau said, adding that around 100 investigators were working on the case and that identity checks in the area would be stepped up.

"In the first case, the victim was shot in the body several times while in the other three cases we have deaths caused by a shot to the head," she said.

On Thursday, a woman of Algerian origin was shot dead in the foyer of her apartment block, part of a working-class housing estate in the Grande-Borne district of Grigny, south of the capital.

She was a widow who worked at Orly Airport and lived with her 18-year-old son.

"Everyone is in shock," said one of her neighbours, who asked not to be named. "She didn't feel threatened. She's a normal person, simple, no history."

She died in hospital after being shot with the small-calibre weapon, which is not widely used by the criminal milieu as it must be fired at relatively close range to be effective. The first victim was a 35-yearold laboratory assistant who was also shot dead in her building in Grigny on Nov. 27.

A man who said he was her exboyfriend turned himself in, was arrested and charged, but has since withdrawn his confession.

On Feb. 22, one of the first victim's neighbours, a 52-year-old man, was shot dead in their building's car park. Then, on March 19, an 81-yearold man was killed by a shot to the head with a weapon of the same calibre in the entrance to a similar block of flats in Grigny's neighbouring suburb of Ris-Orangis.

"No link has been made between the four victims except for the fact that the second lived in the same building at the first," Le Queau said.

Gueant noted the man arrested in connection with the first killing was in jail during the latest attack.

"That said, this series is worthy of all our attention and we have put all our means at our disposal behind it," Gueant said.

Last month, the southern city of Toulouse was shocked by a string of seven killings by Mohamed Merah, a 23-year-old Frenchman from an Algerian family who declared himself to be a supporter of the al-Qaida militant network. Merah killed three off-duty paratroopers, three Jewish schoolchildren and a trainee rabbi before he was cornered in his apartment and killed in a shootout with police