Spain's Prime Minister Mariano Rajoy (2nd L) walks with Development Minister Ana Pastor (bottom) and Galician regional president Alberto Nunez Feijoo (L) as they tour the wreckage of a train crash near Santiago de Compostela, northwestern Spain, July 25, 2013. [Photo/Agencies]

MADRID - Spain's Prime minister Mariano Rajoy on Thursday said he would declare three days of official mourning after a train derailed in the northwestern region of Galicia, killing at least 78 people and injuring up to 131.

"I will sign a decree to declare three days of official mourning in all Spain," Rajoy told journalists after visiting the Santiago de Compostela hospital where most victims were taken.