Daniel Schweimler: An emotional issue

But Spanish officials say the prisoners will not be moved until it is convinced that the ETA, the Basque separatist movement, has abandoned violence permanently.

The protesters, led by relatives of the prisoners, want more than 500 imprisoned ETA members transferred to the Basque region, following a ceasefire declared by the ETA in September.

Some of the prisoners are as far away as the Canary Islands, with others held in Madrid and in southern Spain.

The strategy of the Spanish authorities has been to keep them away from the Basque region and their main source of political support.

But the families say the situation places an unfair burden on them, forcing them to travel hundreds of kilometres to visit their relatives.

Basque nationalist politicians and trade union representatives joined the families on the demonstration.

Negotiation issue

The future of the prisoners will be one of the first and most important issues on the negotiating table if peace talks between the ETA and the Spanish government get under way.

Those calling for the prisoners to be moved say it would be a symbolic gesture by the government, proving its commitment to the peace process which ETA says it started with its September ceasefire to its 30-year conflict.

In October, the government said it would move four inmates back to the Basque region for what it called humanitarian reasons. All were sick, and had already served a large proportion of their sentences.

The organisers of the demonstration believe the government's move does not go far enough.