(S (S (S (BASENP (DT No) (NN group)) (VP (VBZ has) (VP (VBN claimed) (BASENP (DT the) (NN attack))))) (CC but) (S (BASENP (JJ Spanish) (NNS sources)) (VP (VBD said) (SBAR (S (BASENP (DT the) (NN attack)) (VP (VBD was) (VP (ADVP (RB probably)) (VP (VP (VBN carried) (PRT (RP out))) (PP (IN by) (NP (NP (BASENP (DT the) (NNP Basque) (NN separatist) (NN group)) (COMMA ,) (VP (VP (VBN considered) (PP (IN as) (BASENP (DT a) (NN terrorist) (NN group)))) (PP (IN by) (NP (BASENP (JJ European) (NNP Union)) (CC and) (BASENP (NNP United) (NNPS States)))))) (COMMA ,) (BASENP (NNP ETA)))))))))))) (PERIOD .))