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.

* PRESSURE BUILDS FOR PEACE:

-- ETA has been under pressure in recent years with more than 750 suspected members detained since 2000. A raid in France in 2004 rounded up ETA's then "top leader", Mikel Antza.

-- On March 20 2006, ETA claimed responsibility for a spate of recent attacks, including five bombs planted on northern Spanish motorways earlier that month to coincide with a regional general strike called by Batasuna.

-- Two days later ETA declared a permanent ceasefire. In late June 2006, Zapatero told parliament he would seek to start peace talks with ETA.

* RETURN TO VIOLENCE?

-- A car bomb exploded at Madrid's airport last December, killing two and prompting Zapatero to break off the peace process.

-- In February, Zapatero dismissed an offer from Arnaldo Otegi, leader of Batasuna, that ETA would not demand major concessions from Spain to restart peace talks.

-- In April, ETA offered in an interview to make new commitments to the stagnated peace process if Spain stopped its "attacks" in the Basque region. ETA had blamed the Socialist government and the moderate Basque Nationalist Party for the blockage of the peace process.

-- On June 5, ETA said it would end its 15-month-old ceasefire.

-- On August 24, a suspected ETA bomb slightly wounded two police officers in the Basque town of Durango.

-- In September, ETA vowed to keep up bomb attacks on the Spanish state, saying last year's peace talks showed there was no point in negotiating with the Socialist government.