(S (S (S (BASENP (PRP It)) (VP (VP (VP (VP (VBZ is) (RB not)) (ADVP (RB yet))) (ADJP (JJ clear))) (SBAR (WHNP (WP who)) (S (VP (VBZ is) (ADJP (JJ responsible))))))) (CONJP (COMMA ,) (CC but)) (S (BASENP (JJ Turkish) (NNS authorities)) (VP (VBP suspect) (NP (NP (BASENP (DT the) (NNP Kurdistan) (NNPS Workers) (NNP Party)) (PRN (LRB -LRB-) (BASENP (NNP PKK)) (RRB -RRB-))) (COMMA ,) (BASENP (DT a) (JJ Kurdish) (NN separatist) (NN group)))))) (PERIOD .))