(S (S (BASENP (NN Twelve) (JJ foreign) (NNS sailors)) (VP (VBD were) (VP (VP (VP (VBN released) (PP (IN by) (BASENP (JJ Nigerian) (NNS gunmen)))) (BASENP (NN today))) (COMMA ,) (PP (IN after) (NP (NP (BASENP (DT an) (NN incident)) (PP (IN on) (BASENP (NNP Friday)))) (SBAR (WHADVP (WRB when)) (S (BASENP (PRPD their) (NN ship)) (VP (VBD was) (VP (VBN attacked)))))))))) (PERIOD .))