Spain's conservative Prime Minister Mariano Rajoy on Monday said he backed aid for Greece but not without "responsibility" and reforms on Athens' part, a day after Greeks voted decisively against more austerity in a referendum.

"What matters is that Greece knows we are willing to help... but the key is that in exchange the reforms necessary for growth and job creation are carried out," Rajoy said. "Solidarity, yes, but that has to be accompanied by responsibility."