Britain has welcomed progress by Greek police in tackling the guerrilla group which killed British military attach� in Athens, Brigadier Stephen Saunders.

Greek authorities said they had tracked down the main hideout and detained one suspected member of November 17, one of Europe's most elusive guerrilla groups.

The brigadier was one of November 17's 23 victims

A Foreign Office spokesman said: "We are obviously encouraged by these developments, which are positive and significant."

The group is named after a bloody student uprising against the ruling Greek military junta in 1973, and has killed 23 people since emerging in 1975, including several British, US and Turkish diplomats.

The 52-year-old brigadier was shot in an ambush as he drove to the British Embassy in Athens in June 2000.

He was fired on through the passenger window of his official car after two men on a motorcycle pulled alongside in halted traffic.

Pleased at progress: Heather Saunders

Weapons used in the attack were found in the cache, police said.

Britain's ambassador to Athens David Madden said his staff had been in contact with Brigadier Saunders' widow, Heather, who was also pleased by news of the breakthrough.

"She is naturally very pleased," Mr Madden told BBC radio.

"She has played a very large role here in the campaign to bring home to the Greek public the reality of murders such as those committed by N17 and the killing of her husband."

The co-operation on the investigation between Greek and British police, who were sent to Athens to help with inquiries after Saunders was murdered, was also praised by the Foreign Office.

Police sources said US and British officials were involved in planning of Thursday's operation, but did not participate in the raid itself.