FACTBOX: Who are Basque separatist group ETA

(Reuters) - A car bomb exploded in the northern city of Bilbao in Spain's Basque Country on Tuesday, badly injuring a man who worked as a bodyguard for a local politician, police and government officials said.

There was no immediate claim of responsibility for the bombing, but it came just days after a judge arrested most of the top leaders of radical separatist party Batasuna, which is banned for links to ETA guerrillas.

Following are some facts about ETA:

* WHAT IS ETA?

-- ETA (Euskadi Ta Askatasuna, or Basque Homeland and Freedom in the Basque language) is fighting for an independent Basque state in northern Spain and southwestern France.

* YEARS OF MAIN ACTIVITY:

-- The group has killed more than 800 people since 1968, typically using car bombs or shootings. The number of ETA killings had fallen from 23 in 2000 to three in 2003. A car bomb at Madrid airport on December 30, 2006 which killed two people, was the first time ETA had killed anybody since May 2003.

-- Spain, the United States and the European Union have listed ETA as a terrorist organization. Former Spanish Prime Minister Jose Maria Aznar, who survived an ETA attack while he was opposition leader in 1995, made eliminating the group a priority. His socialist successor, Jose Luis Rodriguez Zapatero, and his government tried and failed to sign a peace deal with ETA, breaking off peace talks after the airport bombing.

-- In 2002, the Spanish parliament passed a law which effectively banned the Basque political party Batasuna, which it described as ETA's political wing. The party denies the allegation.