"Shocked and saddened by the news coming from Gaza and the many civilian casualties following the Israeli airstrikes last night," said Costa, who heads the body representing the bloc's 27 states.
"Violence must stop and the terms of the ceasefire agreement must be respected. All hostages and detainees must be released, and humanitarian aid must be resumed immediately," he wrote on X.
The health ministry in Hamas-run Gaza said more than 400 people were killed after the strikes.
Earlier the EU's aid chief called the fresh violence "devastating".
"Civilians have endured unimaginable suffering. This must stop," commissioner Hadja Lahbib wrote on X, adding: "It is imperative to return to a ceasefire immediately".
Saudi Arabia condemns Israel Gaza strikes 'in strongest terms'
Saudi Arabia on Tuesday condemned Israel's bombing of "unarmed civilians" after more than 400 people were killed in Gaza, according to the health ministry in the Hamas-run territory.A foreign ministry statement voiced "Saudi Arabia's condemnation and denunciation in the strongest terms of the Israeli occupation forces' resumption of aggression... and their direct bombardment of areas populated by unarmed civilians".
France condemns Israeli strikes on Gaza, urges 'immediate' end to hostilities
France on Tuesday condemned Israel's renewed strikes on Gaza and urged an "immediate" end to the hostilities it says are endangering efforts to free the Israeli hostages held by Hamas and the lives of Palestinian civilians. "France condemns the Israeli strikes carried out since yesterday on the Gaza Strip, which have caused numerous civilian casualties," the French foreign ministry said after the strikes which killed 413 people according to the health ministry in the Hamas-controlled territory. "France calls for an immediate end to hostilities, which are jeopardising efforts to free the hostages and threatening the lives of the civilian population in Gaza," it added.Russia condemns Israel's renewed strikes on Gaza
Russia on Tuesday condemned Israel's renewed bombardment of the Gaza strip, the deadliest since a fragile ceasefire between Israel and Hamas took effect in January."Moscow deeply regrets Israel's resumption of its military operation in the Gaza Strip," the Russian foreign ministry said. "Russia strongly condemns any action that leads to the death of civilians and destruction of social infrastructure." The Kremlin said earlier it was concerned the strikes would lead to a "spiral of escalation". "We are monitoring the situation very closely and, of course, we are waiting for it to enter a peaceful course again," spokesman Dmitry Peskov told reporters.
