A Moroccan imam believed to have radicalised youths who committed Spain's terror attacks was confirmed dead Monday in an accidental explosion at the suspects' bomb factory, police said.

Asked whether Abdelbaki Es Satty had died in the blast on Wednesday that precipitated the attacks, Catalan police chief Josep Lluis Trapero said: "It is confirmed," adding "the remains of the imam were there", in the house in Alcanar that exploded.