The Basque separatist group Eta has announced a permanent ceasefire in its fight for independence from Spain.
In a video statement sent to the media, the group said the truce would be "internationally verifiable".
But the Spanish government has rejected Eta's statement, saying it contained nothing new.
Eta's campaign for independence for the Basque region has cost more than 800 lives since 1968 but it called a halt to armed attacks last year.
As in previous filmed statements, the video showed three Eta militants in white hoods. They said it was "time to act with historical responsibility".
However, they made no mention of disarming or dissolving the organisation - key demands of the Spanish government.
Speaking a few hours after the statement was released, Spain's Interior Minister Alfredo Perez Rubalcaba said Eta remained "as arrogant as ever".
He said the statement was not bad news but was not what the country had been hoping for.
Eta had once again failed to declare a definitive and irreversible end to violence, he said.
In the video, the Eta members said the organisation was declaring "a permanent and general ceasefire which will be verifiable by the international community".
"This is Eta's firm commitment towards a process to achieve a lasting resolution and towards an end to the armed confrontation," said the statement.
Eta said it would continue its "indefatigable struggle" for a "truly democratic situation in the Basque Country".
There was no explicit reference to the group giving up its arms, which has been a key demand of the government.
"From reading their statement, we can see that we are dealing with an Eta that has the same aims as always," Mr Rubalcaba said.
"It's an Eta that has a distorted view of reality, that has a list of demands that it's not abandoning. In summary: it's an Eta that displays the same arrogance as always, plus the usual discourse."
The BBC's Sarah Rainsford in Madrid says the strong language in the statement goes further than Eta has before, particularly the claim that the truce would be "verifiable", which could indicate a willingness to disarm.
Spain's socialist government has been wary of Eta's claims since the last truce was broken by a bomb attack at Madrid's Barajas airport in December 2006, says our correspondent.
That attack resulted in peace talks being called off.
In September last year, Eta announced an end to its armed offensive but the government said the move was too weak for negotiations to restart.
The government argues that the militant group has been seriously weakened by the arrest of most of its key leadership in recent years.
It has also come under pressure from its political wing, Batasuna, which has been outlawed because of its connections to Eta but wants to be able to take part in local elections later this year.