US Democratic representatives Brian Baird and Keith Ellison expressed shock at the plight of the war-shattered Gaza
"The amount of physical destruction and the depth of human suffering here is staggering" Baird said in a statement issued jointly with Ellison during their visit which coincided with a similar trip by US Senator John Kerry.
The visits were the first by US lawmakers since Hamas, an Islamist movement Washington blacklists as a terrorist organisation, seized control of the overcrowded territory in June 2007.
Ellison, a representative from Minnesota, harshly criticised restrictions on the delivery of desperately needed goods into the coastal strip that has been under a crippling Israeli blockade imposed after the Hamas takeover.
"People, innocent children, women and non-combatants, are going without water, food and sanitation, while the things they so desperately need are sitting in trucks at the border, being denied permission to go in," he said.
"The stories about the children affected me the most," said Ellison. "No parent, or anyone who cares for kids, can remain unmoved by what Brian and I saw here."
Baird, from Washington state, said the situation he saw was "shocking and troubling beyond words."
"The personal stories of children being killed in their homes or schools, of entire families wiped out, and relief workers prevented from evacuating the wounded are heart wrenching," he said.
Ellison, the first Muslim elected to the US
"However, the arbitrary and unreasonable Israeli limitations on food, and repair and reconstruction materials are unacceptable and indefensible," he added.
Ellison and Bair both stressed that their visit did not have the official sanction of the Obama administration.
They said they held talks with civilians and relief workers, while Palestinian officials stressed they did not meet with any representatives of Hamas.
During their visit, the pair visited Izzbet Abed Rabbo, a community in northern Gaza devastated during the deadly 22-day Israeli offensive that ended on January 18.
An estimated 14,000 to 20,000 homes and other buildings were damaged or destroyed during the military offensive in which more than 1,300 Palestinians were killed.
"The first and most urgent priority must be to help the people in Gaza. At the same time, the rocket attacks against Israeli cities must stop immediately," Baird and Ellison said in their joint statement.
"Just as the people of Gaza should not be subject to what they have experienced, the Israeli civilians should not have to live in fear of constant and indiscriminate rocketing," they added.
On Friday, the two planned to tour the Israeli towns of Sderot and Ashkelon, which are regularly targetted by the almost daily rocket attacks from Gaza.