Spain train bomb victims remembered
The ceremony in Madrid's Almudena Cathedral was one of several events held around the city in homage to the 191 people killed and nearly 2,000 injured in the attacks.
Elsewhere, people laid flowers and lit candles at the train stations and sites of the bombings.
The attackers targeted four commuter trains with 10 shrapnel-filled bombs concealed in backpacks during morning rush hour on March 11, 2004.
Twenty-eight people, mainly from North Africa, went on trial in 2007 and 18 were convicted of taking part in the attacks.
The seven alleged ringleaders of the attacks blew themselves up three weeks after the bombings as police closed in on their apartment hide-out in a Madrid suburb.
"It was so traumatic all that happened, I think that you remember it every day," said Maria Blanco, 45, a cleaner. "I think that every time you get on a train you remember."
The militants who claimed responsibility for the bombings said they carried out the attacks in revenge for the Spanish government's support for the Iraq war and troop presence in Afghanistan.
The conservative Popular Party government in power at the time repeatedly pointed to Basque separatists as prime suspects in the bombings, even after evidence of Islamic involvement emerged.
The party was defeated in general elections held three days after the attacks.