The leader of the banned Basque Party Batasuna, is too ill to appear in court.
Arnaldo Otegi has not come before a judge as planned, because doctors confirm he has flu and is unable to speak. He was due to answer questions which could lead to imprisonment, over a series of bombings in northern Spain last week.
Two bombs exploded in Cantabria and Navarra.
A strike in the Basque country had been called by Batasuna on the same day.
The protests were against the regional government’s refusal to allow tributes to be paid to two Eta-linked prisoners who died in jail. One committed suicide, the other suffered a heart attack.
Activists condemned the conditions in which they were detained.