The Basque militant group Eta says it will hand over all its weapons on Saturday – but warns that its enemies might still block the process.

The pledge came in a letter obtained by the BBC, confirming earlier reports about Eta disarmament plans.

Eta killed more than 800 people and wounded thousands in over 40 years of violence aimed at Basque independence.

Eta declared a ceasefire in 2011 but did not disarm. Spain refuses to negotiate with the armed group.

The letter, dated 7 April, says that “after giving up all its weaponry (arms and explosives) to Basque civil society representatives [Eta] now is a disarmed organisation”.

But further on it warns that “the process is not completed” and “‘disarmament day’ is tomorrow”.

“We want to warn that still the process can be attacked by the enemies of peace. The only real guarantee to succeed are the thousands of people gathering tomorrow in Bayonne [south-western France] supporting the disarmament.”