Spanish Interior Minister Alfredo Perez Rubalcaba held the Basque separatist group ETA responsible for a car bomb attack that injured 17 people Thursday in the northern Spanish city of Pamplona, reported dpa.
The vehicle exploded in a car park in the grounds of the University of Navarra in Pamplona, capital of the Navarra province which borders on the separatist Basque region.
The Spanish official said that the blast was likely to have been in retaliation for Tuesday's arrest of four suspected ETA members in Pamplona who were thought to have been planning an attack in the region.
Between 80 to 100 kilos of explosive was used in the attack. More than 20 parked vehicles were damaged in the blast, and nearby buildings were substantially damaged.
State-owned radio station RNE reported that the injured mostly suffered from lacerations caused by flying shards of glass, while some complained of hearing damage.
Police evacuated university buildings and cordoned the area off following the blast.
An anonymous caller had warned of the blast to police one hour before it detonated, but the caller did not say what city the bomb was to be found.
Police initially searched for the bomb on the university campus in the Basque capital Vitoria - over 100 kilometres from Pamplona.
RNE radio quoted a University of Navarra spokesman as saying it was a "great wonder" that no one was killed in the attack, as the campus was thickly populated at the time.
Spain's Crown Prince Felipe condemned the attack, saying "the terrorists will not succeed in changing our democratic system."
ETA is listed as a terrorist organization by the European Union and the United States.
Bomb and arson attacks believed to be the work of ETA damaged two train stations in Spain's Basque Country on Saturday, without causing injuries.
The University of Navarra has been the target of ETA terrorist attacks six times previously. Founded in 1952 as the first private university in Spain, the institution is closely identified with the Catholic lay organization Opus Dei.
The school's founder was Opus Dei founder Josemaria Escriva de Balaguer, who was canonized by the Catholic Church six years ago.