Gaza City (afp) — Rescuers said an Israeli strike on Monday killed at least 20 people at a Gaza school sheltering displaced people, as Israel steps up what it calls an offensive to destroy Hamas.

The intensified violence, after a nearly three-month blockade of humanitarian supplies into the Gaza Strip, has sharpened international condemnation of Israel.

World leaders meeting in Madrid at the weekend called for an end to the “inhumane” and “senseless” war, while humanitarian organizations said the trickle of resumed aid is not nearly enough to staunch the hunger and health crises.

In Gaza City, civil defense agency spokesperson Mahmud Bassal said that “at least 20 martyrs” were transported to hospital, most of them children, and 60 people were wounded in the “horrific occupation massacre at the Fahmi al-Jarjawi school” at dawn, where hundreds of people were sheltering, referring to Israel.

The Israeli military said it had “struck key terrorists who were operating within a Hamas and Islamic Jihad command and control center embedded in an area that previously served as the ‘Faami Aljerjawi’ School in the Gaza City area,” adding that “numerous steps were taken to mitigate the risk of harming civilians.”

The day before, Israeli strikes killed 22 people and wounded dozens more across the Palestinian territory, the agency said.

Israel has expanded its Gaza offensive, activating tens of thousands of reservists as it aims for “the defeat of Hamas.”

US President Donald Trump, whose administration has strongly backed Israel in its campaign, on Sunday said he wanted to “see if we can stop that whole situation as quickly as possible.”

The same day, as Arab and European nations gathered to seek an end to the conflict, Spanish Foreign Minister Jose Manuel Albares called for an arms embargo on Israel.

He also called for humanitarian aid to enter Gaza “massively, without conditions and without limits, and not controlled by Israel,” describing the territory as humanity’s “open wound.”