Key dates in the history of the armed Basque separatist movement ETA, western Europe's last major armed secessionist group, which is blamed for 829 deaths over four decades.

31 July 1959: ETA is formed during the dictatorship of General Francisco Franco by a group of Basque nationalist students.

7 June 1968: ETA shoots dead the police chief of the Basque city of San Sebastian -- the first deadly attack for which it claimed responsibility.

20 December 1973: Luis Carrero Blanco, Franco's prime minister and presumed successor, is blown up in his car - one of ETA's most notorious attacks.

19 June 1987: ETA stages its deadliest bombing, killing 21 shoppers at a Barcelona supermarket car park and injuring 45 others.

12 June 1997: ETA shoots dead a conservative town councillor in the Basque country. Millions take to the streets in protest.

24 March 2006: ETA declares a "permanent ceasefire" in return for talks with the government.

30 December, 2006: ETA claims responsibility for a bombing at Madrid airport that kills two people, breaking the ceasefire.

30 July 2009: Two police officers are killed by a bomb under their car on the island of Majorca - ETA's last deadly attack in Spain.

10 January 2011: ETA declares a permanent ceasefire. Spain's Socialist government rejects it, demanding a definitive end to violence.

20 October 2011: ETA announces "the definitive end to its armed activity", but declines to formally disband or disarm.

24 November 2012: ETA says it may discuss disbanding if jailed members are moved to prisons nearer home. Spain and France refuse to negotiate.

23 February 2013: Basques launch a new pro-independence party, Sortu, born from the ashes of Batasuna which was outlawed for links to ETA.

7 May 2013: The group's "logistical core" is broken up by arrests in France. Only a few dozen active members are thought to remain at large.

21 October 2013: The European Court of Human Rights prompts the release of dozens of jailed ETA members by upholding their right to early release.

28 December 2013: Jailed ETA members abandon their long-held demand for an amnesty in an apparent bid for concessions from authorities.

11 January 2014: Rival Basque political parties join together in a demonstration supporting demands for concession on prisoners.

21 February 2014: International monitors say ETA has started to put its arms beyond use - hailed as a key step towards its disbandment.