Seven explosions have been reported at different locations around Spain.
The blasts follow a threat by Basque separatist group ETA to detonate up to seven bombs at undisclosed locations around Spain this afternoon.
Spanish explosive experts inspect the scene of a blast in the northern Spanish town of Santillana del Mar.
The bombs are reported to have exploded in Leon, Avila, Cuidad Real, Malaga, Valladolid, Alicante and Santillana del Mar.
The explosions were said to have been relatively small, but two or three people were slightly wounded in the explosion in the northern coastal city of Santillana del Mar.
The Basque Garanewspaper website reported the threats, saying the group planned to detonate the bombs at 12.30 GMT.
Before the blasts, the Interior Ministry had said the seven sites targeted - streets and plazas and a parking lot - had been evacuated and cordoned off.
ETA set off five bombs simultaneously in Madrid last Friday night, the group's first serious attack in the capital in two years. Another small bomb was defused in the southern town of Almeria last Saturday.
Today is the anniversary of the introduction of Spain's 1978 constitution. ETA, which has killed more than 800 people in a 36-year campaign for Basque independence, opposes the constitution for enshrining the Basque country as part of Spain.