The placards held aloft by the elderly marchers in Bilbao's Albia Gardens are neatly matched, each with an identically sized photograph in a green frame on a painted wooden stick.

About 50 protesters walk slowly in two disciplined lines under the towering plane trees of this well-tended city centre square.

They are mostly stern-faced women, though one old man has a black Basque beret stretched across a balding head.

It is a peaceful protest, largely ignored by the office workers and shoppers resting on the square's benches. The faces on the placards, however, are a reminder of violence.

They are the faces of Eta - the Basque separatist group that has killed 800 people in bombings and shootings over the past four decades.

The people in the photographs are jailed sons, daughters, husbands, wives and siblings. The older, grainy black-and-white pictures are mostly of men, some with the hairstyles and bushy moustaches of the era in which they were jailed.

The more recent ones, the younger faces, include many more women. They are among the 750 people now in prison for Eta-related crimes. Others are still at large, keeping Europe's last blood-soaked separatist conflict alive in the western borderlands of Spain and France.

And increasingly, they are women.

Somewhere across the French border, Eta's clandestine leadership is being reformed after a series of arrests. In the last few days a series of bomb blasts has sent Madrid and Europe a chilling reminder that the separatist group remains active and deadly.

This week, two police officers on the Spanish resort island of Mallorca were killed when a bomb wrecked their patrol car.

Less than 36 hours earlier, a car bomb destroyed a police barracks in the northern Spanish city of Burgos, injuring about 60 people.

In June, Inspector Eduardo Puelles, a senior anti-terrorist police officer, was burnt to death in the Bilbao suburb of Arrigorriaga, after a bomb attached to the underside of his car turned it into a ball of flames and molten metal. Neighbours who heard his cries said there was nothing quick or easy about his death. "Get me out of here! Get me out!" he had screamed.

Police believe his murder may have been ordered by one of two women, Iratxe Sorzabal or Izaskun Lesaka, who are thought to hold senior positions in Eta's increasingly fragile military apparatus.

For most Spaniards, Eta members are blood-thirsty, cold-hearted terrorists.

"They haven't achieved anything by murdering my husband. They don't defend anyone's freedom, in fact they just restrict it," Puelles' widow, Paqui, told a crowd of 25,000 people who marched through Bilbao to express their revulsion the day after his murder. "This is the only thing they know how to do: kill, kill and kill."