Washington firmly backed Israel and condemned Palestinian terror groups Saturday after a heavy round of fighting broke out in the restive Gaza region, with hundreds of rockets shot at the Jewish state, leading to massive retaliatory airstrikes.

“The United States strongly condemns the ongoing barrage of rocket attacks by Hamas and Palestinian Islamic Jihad from Gaza upon innocent civilians and their communities across Israel. We call on those responsible for the violence to cease this aggression immediately,” State Department spokesperson Morgan Ortagus said in a statement.

“We stand with Israel and fully support its right to self defense against these abhorrent attacks,” she added.

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Over 250 rockets were shot at Israel by Hamas and Islamic Jihad Saturday, the most serious round of violence in months. A man was killed in the Israeli city of Ashkelon and three more Israelis were injured, including an 80-year-old women seriously hurt in Kiryat Gat.

Six Palestinians were reported killed, including four fighters. A mother and her year-old baby were also killed, but Israel insisted it was not responsible and that the two were killed by a failed rocket launch.

US Special Envoy Jason Greenblatt also condemned Hamas and backed Israel on Twitter.

“Hamas & PIJ have engaged in yet another deplorable act of terrorism, indiscriminately firing hundreds of rockets at Israeli civilian communities. The U.S. stands firmly in support of Israel’s right to self-defense and we call on the international community to do the same,” he tweeted.

He added that the Gazan groups were hurting Palestinians.

When Hamas and PIJ continue to choose terrorism, they prevent the world from trying to help the Palestinians in Gaza and they cause harm to Palestinians. — Jason D. Greenblatt (@jdgreenblatt45) May 5, 2019

The European Union’s ambassador to Israel, Emanuele Giaufret, sharply criticized the rocket attacks on Twitter, saying “firing indiscriminately against civilians (is) unacceptable.”

The United Nations‘s Mideast envoy, Nickolay Mladenov, said the UN was working with Egypt to restore calm and called on all sides to “deescalate” and restore recent understandings.

“Those who seek to destroy them will bear responsibility for a conflict that will have grave consequences for all,” he said in a statement.

The flareup comes as the US is preparing to roll out its Israeli-Palestinian peace plan next month.

The proposal is thought to include major economic improvements to Gaza as part of an international effort to rehabilitate the beleaguered enclave, currently ruled by the Hamas terror group.

Greenblatt, who has frequently sparred with Palestinian officials on social media, has been a strident critic of Hamas and Islamic Jihad.

Israel and Palestinian terrorists in the Gaza Strip have fought three wars since 2008 and fears remain of a fourth.

A ceasefire between Israel and Hamas brokered by Egypt and the United Nations had led to relative calm around Israel’s April 9 general election.

But the past week saw a gradual uptick in violence.

With the ceasefire at risk, a Hamas delegation led by its Gaza head Yahya Sinwar went to Cairo on Thursday for talks with Egyptian officials.

Israel and Egypt have maintained a crippling blockade on Gaza since Hamas, which seeks to destroy Israel, seized control of the territory in 2007. Jerusalem says it is necessary to prevent terror groups from rearming and becoming an even greater menace.

Agencies contributed to this report.