Thousands of pro-Palestinian protesters gathered in the US capital on Saturday, marching past the White House to chants of "Free Palestine" as the death toll continued to climb in the conflict between Israel and Hamas.

"What is happening today is just beyond the pale. It's so upsetting, we are watching people being killed by an army that this country supports," demonstrator Linda Houghton told AFP.

Across the country, Americans have held pro-Israel and pro-Palestinian protests in the week since Hamas militants broke through the heavily fortified border between the Gaza Strip and Israel killed more than 1,300 people.

Israel's bombardment of the Gaza Strip in response has killed more than 2,200 people. As on the Israeli side, most of them were civilians.

More than one million people in the northern part of the crowded enclave have been ordered to flee ahead of an expected Israeli ground assault, an exodus that aid groups said would worsen the humanitarian disaster.

Israel has also cut off food, water and electricity supplies to Gaza's 2.4 million people.

Clashes in the occupied West Bank have killed 53 Palestinians in the past week. 

"I wish we could all do something, I wish we could stop the war, just stop the war," said Ahmed Abed, one of the protesters marching through downtown Washington under a sea of Palestinian flags.

"They are in prison," he said of the blockaded Gaza Strip.

Signs carried by marchers included messages such as "End the occupation" and "Cease-fire now."

In New York, home to the world's largest Jewish population outside of Israel, hundreds gathered in Brooklyn on Friday in solidarity against Israel's offensive, wielding a banner emblazoned with the message "Jews Say Stop Genocide Against Palestinians."

Jewish New Yorkers have been split, with some voices urging Israel to defend itself and others increasingly warning of Palestinian "genocide."

Two days after the Hamas attack, Arthur Schneier, the longtime senior rabbi at Manhattan's Park East Synagogue, called the assault "the most existential threat to Israel since its founding in 1948," a message that echoed Israeli authorities.

On the other side of the country, more than 1,000 pro-Palestinian demonstrators marched in Los Angeles on Saturday, local media reported. 

Videos on social media showed tense moments between the crowd and pro-Israel counterprotesters.

nro/dva