Several hundred more took part in marches in San Sebastian, a coastal city across the border from France, and the Basque regional capital, Vitoria.

"It is true that it hurts us, that we feel impotent and anger before so much injustice, torture and detentions," Tasio Erkizia, a Basque independence activist, told the crowd during the march in Bilbao.

"But once again they are mistaken, they have been mistaken for years, they believe that they are going to put this people on its knees, but they are not going to do it neither with the carrot nor the stick," he added.

'Pre-election stand' 

Pernando Barrena, a senior Batasuna member still at large, said that the police operation was a "pre-election stand" by the government.

The Socialist party "is looking to improve its position" against the conservative opposition Popular party "before the next general elections in March," he said.

Barrena, who did not participate in Thursday's meeting, was speaking to journalists outside a prison in San Sebastian where Arnaldo Otegi, Batasuna party leader, has been held since June.

Jose Luis Rodriguez Zapatero, Spain's preime minister, will face general elections in March 2008 in which the question of regional autonomy and the Basque conflict are becoming major campaign issues.

The government has taken a hard line against Eta since the armed group officially ended a 15-month-old ceasefire in June.

Suspects questioned

Baltasar Garzon, a leading anti-terrorist judge who ordered the arrests, suspected that the meeting had been planned to transfer power to new leaders of the party after it was weakened by recent arrests, a judicial source said.

"It is true that it hurts us, that we feel impotent and anger before so much injustice, torture and detentions"

Tasio Erkizia, Basque independence activist
The detained members are expected to be transferred to Madrid, where they will be questioned by Garzon over the weekend.

They face charges related to Garzon's investigation into links between Batasuna and Eta - especially the political party's suspected financing of Eta's activities, the source added.

Among those held was Joseba Permach, one of Batasuna's main spokesmen since Otegi's detention in June for the crime of "glorifying terrorism".

Thursday's raid followed the arrests of Joseba Alvarez, Batasuna's international spokesman, and Oihana Agirre, a member of the Basque prisoner support network Askatasuna, on Tuesday in San Sebastian.

Earlier on Friday, Garzon ordered both men remanded in custody. The two are accused of organising an unauthorised demonstration held on September 9 in San Sebastian in favour of Askatasuna.

Tightening the screw

"It is part of a ... tightening of the screw that has been observed since the [end of] truce," Gorka Landaburu, a Basque journalist and commentator, said of Thursday's crackdown.

"Things have changed toward Batasuna. During the peace process [the authorities] didn't intervene, now they intervene."

Both Batasuna and Eta are listed as terrorist organisations by the European Union and the US government.

Batasuna was outlawed by Spain's supreme court in March 2003 on grounds that it was the political wing of Eta, which has been blamed for more than 800 killings since the 1960s in a campaign to establish an independent Basque state from parts of northeastern Spain and southwestern France.

Eta called off a ceasefire after peace talks with the Spanish government broke down. Its last major attack took place in December 2006, when a bomb at Madrid airport killed two people.