WASHINGTON: US President Joe Biden has ordered "additional support" for Israel after the attack by Hamas group, the White House said Sunday, without giving further details.

"The President directed additional support for Israel in the face of this unprecedented terrorist assault by Hamas," the White House said in a statement.

The announcement came after a senior administration official had said on Saturday that high-level discussions between US and Israeli officials on military aid were already underway.

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Biden and Vice President Kamala Harris were briefed by national security officials on the situation in Israel early Sunday and will continue to receive updates, the White House said.

White House officials will also remain in contact with Israelis and "counterparts throughout the region," the statement added.

Biden gave a statement on Saturday pledging "rock solid and unwavering" support for Israel, Washington's key Middle East ally, after the surprise attacks by Hamas which killed more than 600 people on the Israeli side.

Palestinian officials have reported at least 370 deaths in Israeli air strikes on Gaza.