He also expressed solidarity with "the people of Palestine who are experiencing the injustice of war and bombardment".
"Spain's commitment to international law and human rights must be constant and must be coherent," he said. "Europe's should be too."
Sánchez and his government, which officially acknowledged a Palestinian state last year, have been harsh critics of Israel, and last week in Congress the prime minister referred to the country as "a genocidal state".
Israel has strenuously denied accusations of genocide, and its foreign ministry summoned the Spanish ambassador for a formal reprimand over Sánchez's "serious remarks".
At Eurovision, Spain's televote saw the country award Israel maximum points for its song New Day Will Rise by Yuval Raphael. Spain's broadcast network RTVE has since requested an audit of the votes.
Ahead of the Eurovision final on Saturday, RTVE aired a message in support of Palestinians – despite being warned to avoid references to Gaza by the EBU.
Spain's entry, Esa Diva by Melody, finished in 24th place on Saturday night in Basel.
