The total number of victims was higher than in any other terrorist attack in Spain , far surpassing the 21 killed and 40 wounded from a 1987 bombing at a Hipercor chain supermarket in Barcelona . On that occasion , responsibility was claimed by ETA . It was Europe 's worst terror attack since the bombing of Pan Am Flight 103 over Lockerbie , Scotland , in December 1988
Pan Am Flight 103
Pan Am Flight 103
2004 Madrid train bombings