Spanish police arrested four suspected members of the armed Basque separatist group ETA today, police sources said.
Three of the arrests came in the Basque town of Lekeitio and one in the centre of Bilbao in the north of Spain, the largest Basque city.
The police operation was ongoing and could result in further arrests, police sources said.
Today's arrests came after the arrests a week ago of 11 leaders of the Basque political party Batasuna. The Spanish government describes Batasuna as ETA's political wing, but the party denies any link to ETA apart from having similar political goals.
Prime Minister Mr Jose Maria Aznar has taken a first step towards banning Batasuna, which won 10 per cent of the vote in Basque regional elections last year.
ETA has killed over 800 people since 1968 to press its demands for an independent state in Basque areas of northern Spain and southwestern France.
ETA, listed as a terrorist organisation by the European Union and the United States, has claimed responsibility for 39 killings since January 2000, when it resumed violence after a year-and-a-half ceasefire.