WASHINGTON -- The United States on Wednesday sanctioned a group of 10 Hamas members and the Palestinian militant organization's financial network across Gaza, Sudan, Turkiye, Algeria and Qatar in response to the surprise attack on Israel that left more than 1,000 people dead or kidnapped.

Targeted for sanctions by the Treasury Department's Office of Foreign Assets Control are members who manage a Hamas investment portfolio, a Qatar-based financial facilitator with close ties to the Iranian regime, a Hamas commander and a Gaza-based virtual currency exchange.

Treasury Secretary Janet Yellen said the U.S. "is taking swift and decisive action to target Hamas's financiers and facilitators following its brutal and unconscionable massacre of Israeli civilians, including children."

"The U.S. Treasury has a long history of effectively disrupting terror finance and we will not hesitate to use our tools against Hamas," she said in an emailed statement.

The sanctions are financial penalties meant to block access to funds held in the U.S. and to prevent the people and entities from doing business with American people and firms.

Secretary of State Antony Blinken noted that the sanctions are "directed at Hamas terrorists and their support network, not Palestinians."

"Hamas alone is responsible for the carnage its militants have inflicted on the people of Israel, and it should immediately release all hostages in its custody," Blinken said. "The United States will not relent in using all the tools at our disposal to disrupt Hamas terrorist activity."

A Hamas financier and several operatives were sanctioned, the Treasury Department said. Also, a Qatar-based Hamas operative and a Hamas military relations commander, who is believed to have been killed in an airstrike on Tuesday, were sanctioned for having acted on behalf of Hamas, the U.S. said. Additionally, a Gaza-based company that provides money transfer and virtual currency exchange services was hit with sanctions, as was its owner.

The Treasury Department highlighted that Hamas relies on small-dollar donations, including through cryptocurrency. The cryptocurrency tracking firm Elliptic said that "to the extent that Hamas has used crypto in the past, it is a relatively small and alternative source of funding" and has proved vulnerable to detection and disruption.

The White House has said it has yet to uncover information that Iran, the principal financial and military sponsor of Hamas, was directly involved in the multipronged Hamas operation -- the biggest attack on Israel in decades. U.S. officials have said their intelligence does not show a direct role by Iran and have not pointed blame at Tehran.

Treasury Deputy Secretary Wally Adeyemo told reporters on Wednesday that Treasury officials will be travelling to the region in the coming days to further their sanctions work.

Brian Nelson, U.S. Treasury's under secretary for terrorism and illicit finance, said at a Deloitte anti-money laundering conference on Tuesday that the U.S. is renewing its plans to pursue Hamas funding streams and made a call for American allies and the private sector to do the same or "be prepared to suffer the consequences."

"We cannot, and we will not, tolerate money flowing through the international system for Hamas' terrorist activity," Nelson said.

"We want to partner with all willing countries and financial entities to stop Hamas financing," he said, "but to the extent that any institution or jurisdiction fails to take appropriate action, they should then be prepared to suffer the consequences."

The shadowy leader of Hamas' military wing, Mohammed Deif, said the Oct. 7 assault on Israel was in response to the 16-year blockade of Gaza, Israeli raids inside West Bank cities over the past year, increasing attacks by settlers on Palestinians and the growth of settlements, among other reasons.

"Enough is enough," Deif, who does not appear in public, said in the recorded message. He said the attack was only the start of what he called Operation Al-Aqsa Storm, and he called on Palestinians from east Jerusalem to northern Israel to join the fight.

President Joe Biden, who arrived in the Middle East early Wednesday to show support for Israel, has tried to tamp down tensions in the escalating war between Israel and Hamas, but those efforts have faced massive setbacks, including a deadly explosion at a Gaza hospital that killed about 500 people.

There were conflicting claims of who was responsible for the hospital blast. Officials in Gaza quickly blamed an Israeli airstrike. Israel denied it was involved and released a flurry of video, audio and other information that it said showed the blast was instead due to a missile misfire by Islamic Jihad, another militant group operating in Gaza. The Islamic Jihad dismissed that claim. The Associated Press has not independently verified any of the claims or evidence released by the parties.

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This story has been corrected to show Biden arrived in the Middle East early Wednesday, not late Tuesday.