ETA said it had suspended the "armed struggle" in Catalonia in a truce backdated "to 1 January 2004" in its statement broadcast on the Basque station Radio Euskadi.
In the statement also carried on Catalan radio stations, a spokesman for ETA, which has been blamed for the deaths of 816 people in the past 35 years, said the group "wishes to strengthen links between our (Basque and Catalan) peoples."
ETA saw "numerous points in common between Catalonia and the Basque country, two regions oppressed by the French and Spanish states," it added.
The spokesman explained the move by alluding to "the new political situation in Catalonia," which last November elected its first left-wing government in the democratic era that dawned with the end of the Franco dictatorship in 1975.
But Spain's Interior Minister Angel Acebes swiftly dismissed the move, saying the announcement would not alter the government stance on ETA.
"We will pursue our strategy of hunting down ETA on the basis of the law, both in Catalonia and in the rest of Spain," Acebes told Spanish state radio.
"This is a truce which benefits only ETA and it is a trap for democracy," Acebes added.
"This is a truce which benefits only ETA and it is a trap for democracy"
interior minister, Spain
The announcement comes less than two weeks after ETA, fighting for an independent state in the northern Basque region of Spain and parts of southwestern France, warned it would attack tourist areas across Spain all year round.
A wave of attacks last summer injured more than a dozen people at popular east coast resorts but reinforced cooperation between French and Spanish police has led to a wave of ETA arrests.
The conservative Spanish government bitterly opposes plans for greater Basque autonomy by the Basque region moderate nationalist government.
The development comes barely three weeks after the former deputy leader of the Catalan government resigned after admitting to holding a secret meeting in southern France with ETA members.
Josep Lluis Carod Rovira, who fronts the left wing pro-independence Republican Left in the Catalan parliament, in coalition with the Catalan Socialists and a hard left ecologist movement, denied reaching an accord with ETA.
He said he had agreed to the meeting as "I do not want more victims of ETA, nor assassinations or deaths - that's why I spoke with ETA."