A car bomb exploded in a University of Navarre car park in northern Spain yesterday, slightly wounding 17 people, after a warning call in the name of Basque separatist rebels Eta, the government said.

Interior Minister Alfredo Perez Rubalcaba said a telephone call in the name of Basque separatist rebels Eta an hour before the blast had warned of a car bomb left in a university.

But while the caller identified the make and colour of the vehicle the message did not specify the university, and police rushed to a campus in the Basque Country regional capital Vitoria.

The University of Navarre is in the city of Pamplona.

"The result is that we could have had a terrible tragedy in the University of Navarre," Mr Rubalcaba told a news conference.

A pall of smoke billowed over the flaming wreckage of the vehicle used for the bomb, which detonated at around 11 a.m. (1000 GMT), shattering nearby university windows as students sat in class.

The blast came just two days after Spanish police arrested four suspected Eta guerillas they said had been planning attacks in the Navarre region.

Eta has killed more than 800 people in four decades of armed struggle for independence of ancient Basque territories in Spain and France, including Navarre.

Authorities blamed the separatists for two bomb attacks which caused no casualties over the weekend in the Basque Country.