Eta says its initiative will bring the final curtain down on a decades-long armed campaign to gain independence for the Basque country straddling the Spanish-French border.
At a press conference in the French Basque city of Bayonne, a group called the International Verification Commission (IVC) confirmed that it had received a list of arms caches from intermediaries, and this had been handed "to the French authorities."
Earlier, informed sources said Eta had provided French police with a list of 12 caches located in the southwestern French departments, or counties, of the Gers, Pyrenees-Atlantiques and Hautes-Pyrenees, they said.
The list was later revised to eight caches, located in the Pyrenees-Atlantiques.
Founded in 1959, Eta has been blamed for the deaths of 829 people in a string of bombings and shootings dating back to 1968. Thousands more were injured.
In 2011, after a string of arrests among its senior ranks and stirring mass protests after particularly bloody attacks, Eta announced that it had abandoned its armed campaign.
The move did not entail disarmament, though.
It has more recently sought to negotiate its dissolution in exchange for amnesties or improved prison conditions for roughly 350 of its members held in Spain and France, and for current members living under cover.
But both France and Spain have taken a firm line and refused any concessions.
Experts on Eta have previously estimated the group's remaining arsenal comprises 130 handguns and two tonnes of explosives.
The IVC, which was set up to monitor Eta's 2011 ceasefire pledge, is not recognised by either the French or the Spanish governments, but its involvement is supported by the government in Spain's autonomous Basque region.
It lists among its members Ronnie Kasrils, a former minister of intelligence in post-apartheid South Africa; Chris Maccabe, a former senior British civil servant who helped negotiate Northern Ireland's "Good Friday" peace agreement in 1998; and General Satish Nambiar, a former deputy chief in the Indian army with experience of UN peacekeeping in the former Yugoslavia.
The IVC's spokesman, Ram Manikkalingam, a former advisor on the peace process in Sri Lanka, told the press conference in Bayonne that the panel had received the list of caches via "the artisans of peace" -- a French civil society group headed by an environmentalist, Txetx Etcheverry.
French police are on standby to take possession of the weapons, officials have told AFP.
An event is being planned in Bayonne on Saturday afternoon to mark so-called "Disarmament Day," under the theme "We are all artisans of peace."
In Madrid, the government on Friday dismissed Eta's disarmament as a unilateral affair and warned that the group -- which it denounces as a terror organisation --- could expect "nothing" in return.
"It will not reap any political advantage or profit," Inigo Mendez de Vigo, Spain's culture minister and its government spokesman, said.
"May it disarm, may it dissolve, may it ask forgiveness and help to clear up the crimes which have not been resolved."
The governing conservative People's Party staged a "counter-event" late Friday in the Basque city of Vitoria in which there was a ceremony for "the protagonists of Eta's defeat." Relatives of Eta victims took part.