Even by the bloody standards of Northern Ireland's violence, the latest murderous exchange between outlawed Catholic-republican and Protestant-loyalist extremists was unusually vicious. Each side targeted women.

Nine days ago Margaret Cooke, widow of a police officer and mother of three, was shot and critically wounded as she drove home from work in Londonderry. The Irish Republican Army was blamed.Thursday a hooded gunman walked into a mobile candy shop on a Catholic housing estate in Northern Ireland and shot two teenage girls and a man dead at point-blank range. The Ulster Volunteer Force was blamed.

Previously women had been caught in the cross-fire, but this time each side deliberately chose to target them.

Katrina Rennie, 16, and Eileen Duffy, 19, were serving behind the counter of the candy shop in Craigavon, County Armagh, Thursday night, when the gunman walked in and opened fire. The shop's owners had been warned by police, according to reports from Northern Ireland, that they were on a Loyalist death list.

The other victim in the Craigavon shooting was Brian Frizell, 29, an unemployed plumber, who was in the shop.

The Protestant Action Force, a cover name sometimes used by the outlawed Ulster Volunteer Force, claimed responsibility Friday.

"This attack was a direct reprisal for the attack in Londonderry on police widow Mrs. Cooke," it said.

Cooke, whose husband Tom, 52, was shot dead by the IRA four years ago, was ambushed by six gunmen as she left work at Londonderry police station. She received multiple gunshot wounds.

In its coded message to the Press Association in Belfast Friday, the Protestant Action Force sought to justify the Craigavon killings by claiming that Duffy was a known republican activist and the shop's owner a republican killer.

It said: "The PAF gives warning that all republican businesses and their staff and all those who serve or employ republican terrorists or Sinn Fein (the political wing of the IRA) members shall be regarded as legitimate targets until such time that the IRA publicly withdraws its threats of assassination against all Protestants irrespective of their occupation."

It added: "We warn all members of the public to stay away from all businesses owned by and staffed by known republicans.`

The warning mirrors a standing IRA threat that any businesses supporting or supplying British security forces in the province will be regarded as legitimate targets. The IRA has recently stepped up its attacks on executives and businesses as part of its campaign to drive the British out of Ireland.

The Workers Party Friday said that the Craigavon killings were an attempt to heighten tensions at a time when politicians were seeking reconciliation of the "two traditions."

Ken Maginnis, Ulster Unionist member of Parliament, warned that the political talks could provoke "an upsurge of violence" from the extremists.

He urged Brooke to send more British troops to the province, saying: "This latest outrage, with the murder of three more people, is quite dreadful. What it shows is that terrorists from whatever quarter will not be frightened by anything. They must be caught."