Spanish authorities say they have foiled a Basque separatist plot to blow up a train at a Madrid rail station.
One powerful 25-kilo (50 lb) bomb was placed on a train travelling from San Sebastian to Madrid, Interior Minister Angel Acebes said.
A second bomb was seized before it was put on the same train, he added.
Two men were arrested on Wednesday in the Basque region, one of whom was carrying the second bomb in a rucksack, Mr Acebes said.
The train was stopped in the city of Burgos, before it could reach the capital.
Christmas travel
Mr Acebes identified the two people arrested as Gorka Loran Lafourcade and Garikoitz Arruarte Santacruz.
The BBC's Katya Adler, in Madrid, says the Spanish capital is alive with people in streets and in train stations setting off to visit families for Christmas.
She said people hearing the news would be enormously worried.
One of bombs seized was timed to go off around 1555 local time
(1455 GMT) in a central station which would have been packed with travellers, she added.
ETA has suffered from increased co-operation between Spain and France over the last few years since 11 September. This has led to some high profile arrests and less attacks.
The Basque separatists, who have killed nearly 850 people since 1968 in their campaign for an independent Basque state, have attempted to stage Christmas bomb attacks in the capital before.
In 1999 civil guards stopped two vans, each carrying about a tonne of explosive, which police said were destined for Madrid.