A package bomb exploded Wednesday in Madrid's main post office, injuring two workers. Earlier this week, package bombs sent to private homes injured a court official and a retired army officer.
Later, police said they defused a letter bomb sent to a government prosecutor at the national court.No group immediately claimed responsibility for the four attacks, but a police spokesman said the Basque separatist group ETA was the main suspect because it has used package bombs in the past.
The explosions could delay proposed negotiations between ETA and the government, which said Friday it would respond favorably to a six-month end to Basque terrorist attacks.
Police, fearing more bombs, ordered the evacuation of the post office after the explosion, which scattered debris in a first-floor sorting room.