The Minnesota freshman has faced criticism for weeks over her positions on the Jewish state, but it boiled over late Sunday after she reacted to a Republican critic in a tweet.

"It's all about the Benjamins baby," Omar replied, referring to American $100 bills featuring the likeness of Benjamin Franklin.

When a user asked who Omar believes is paying US politicians to support Israel, the former Somali refugee tweeted a one-word response: "AIPAC!"

The exchanges triggered an uproar. Democrat Eliot Engel, chairman of the House Foreign Affairs Committee of which Omar is a member, said: "Anti-Semitism in any form is unacceptable, and it's shocking to hear a Member of Congress invoke the anti-Semitic trope of 'Jewish money.'"

Liz Cheney, a top Republican leader in the House of Representatives, urged Democratic leaders to "condemn this anti-Semitism" and remove Omar from the committee.

Two Democratic lawmakers circulated a letter addressed to Democratic leaders, including House Speaker Nancy Pelosi, urging them to take "swift action" against anti-Semitic language by members.

The letter's authors, representatives Josh Gottheimer and Elaine Luria, who are both Jewish, did not mention Omar by name, but the target of their anger was clear.

"We must speak out when any Member -- Democrat or Republican –- uses harmful tropes and stereotypes, levels accusations of dual loyalty, or makes reckless statements like those yesterday," they wrote.

Omar has been critical of Israel's government over its treatment of Palestinians. She has supported the Boycott, Divestment, Sanctions (BDS) movement which aims to put economic and political pressure on Israel.

Omar and fellow Muslim congressional freshman Rashida Tlaib's support for the boycott has opened a breach in the Democratic Party and threatens to create a fissure in the ironclad US-Israeli alliance.

At least a dozen lawmakers have openly criticized Omar, including Debbie Wasserman Schultz, the first Jewish congresswoman elected from Florida.

Omar's "tweets implying that American support for Israel is driven by money, rather than shared interests and values, are alarming, offensive and disturbing," Wasserman Schultz said.

Last month Omar expressed regret for saying in a 2012 tweet that Israel "has hypnotized the world" while carrying out "evil."