A land mine killed two soldiers serving with the Spanish contingent in Afghanistan on Monday, officials said.
An Iranian interpreter traveling with the Spaniards also died in the attack and three other Spanish soldiers were seriously wounded, Jose Antonio Alonso said.
Alonso said Spain remains committed to the United Nations-led mission in Afghanistan, to which it has contributed some 700 troops, and that he will go ahead Tuesday with plans to ask Parliament to send 52 more Spaniards to help train Afghan forces.
He called it a "mission with a very clear purpose - to rebuild Afghanistan civilly and administratively and keep terrorism from controlling the country."
Monday's attack occurred near the town of Shewan while the soldiers were returning from a patrol mission at the head of a column of five vehicles.
The explosion apparently occurred when the lead vehicle detonated an explosive device with one of its rear wheels, the minister said.
One of the soldiers was Spanish and the other was an Ecuadorean serving with the Spanish contingent. Spain allows people from some Latin American countries to serve in its military forces while retaining their native nationality.
In February, an attack on a Spanish military convoy killed a female soldier and wounded two other troops.
A Peruvian soldier serving with Spanish forces in Afghanistan was killed in an attack on a Spanish convoy in July of last year. Four other soldiers were wounded.