Officials said the attack bore the hallmarks of ETA

A car bomb explosion has killed two policemen and injured at least two other people in a town in northern Spain.

The explosion occurred around 1225 (1025 GMT) in a square in the town of Sanguesa in Navarra province, the capital of which is Pamplona.

Officials said the bomb attack bore the hallmarks of the Basque separatist group, ETA.

It follows Sunday's municipal elections, the first since Madrid banned the radical separatist party Batasuna on the grounds it formed part of ETA, listed as a terrorist group by the US and European Union.

"ETA has murdered once again," Deputy Prime Minister Mariano Rajoy said in Madrid, vowing to use "all means at our disposal" to fight the group.

Visit called off

The president of the Navarra regional government, Miguel Sanz, said the bomb may have been attached to the underside of the police vehicle, a mobile unit renewing identity cards in the town.

Spanish Prime Minister Jose Maria Aznar immediately cancelled a planned visit to Russia.

Navarra borders the troubled Basque region and is home to many Basque nationalists.

ETA is waging a bloody campaign for independence for the seven regions in northern Spain and south-western France that Basque separatists claim as their own.

Its shootings and killings have killed more than 800 people since the late 1960s.