Millions of Spaniards observed a five-minute silence at midday local time to mark the first anniversary of the Madrid train bombings in which 191 people were killed and another 1,900 were injured.
Commemorations took place throughout the country, but most services were held in Madrid, where King Juan Carlos opened a park of remembrance.
Earlier this morning, some 650 churches in the Spanish capital started ringing their bells at 7.37am, the precise moment when the first of ten explosions went off aboard four commuter trains.
World leaders led by UN Secretary General Kofi Annan and hundreds of security experts have meanwhile gathered in Madrid to reflect on the attacks carried out by Islamist militants three days before a general election.
Voters in that election gave the opposition Socialists victory in an upset that political analysts partly attributed to the way the Spanish conservative government had initially wrongly blamed the Basque separatist group ETA for the bombings.
The attacks also reminded voters of the government's unpopular decision to send troops to Iraq.
Socialist Prime Minister Jose Luis Rodriguez Zapatero ordered the troops home immediately after taking office.
