Basque militant separatist group ETA will announce plans to disarm on Friday, France's Le Monde newspaper reported, saying a full handover of weapons was scheduled for April 8.
The Basque government said regional leader Inigo Urkullu was due to comment on the news at 2 p.m. (1300 GMT). Spain's Interior Ministry declined to comment.
"ETA has handed us responsibility for the disarmament of its arsenal and, as of the evening of April 8, ETA will have completely handed over its weapons," Txetx Etcheverry, an activist with environmental campaign group Bizi, was quoted as saying in Le Monde. Bizi is a pro-Basque independence association.
ETA, which has killed more than 800 people over several decades through bombings and assassinations, called a unilateral ceasefire in 2011 and has pledged to turn in its weapons, though a full handover has not yet happened.
The group has been severely weakened in recent years after hundreds of its members, including its leader, were arrested and police seized several of its weapons stashes.