"Israeli settlers, brandishing American made M4s, detained me & other Americans on my trip to Palestine," Khanna wrote on his Instagram account.
Khanna added when "IDF arrived, they sided with the settlers and continued out detention. They made a huge mistake."
"I saw the arrogance in the eyes of those settlers, 21- and 22-year-olds with guns, laughing that they had detained us, the arrogance of those young IDF soldiers that my tax dollars are funding, having no respect for the fact that they were detaining Americans, no respect that there was an American congressperson in that bus, and laughing when our translator told them that there are Americans there and the American embassy is concerned," Khanna told Reuters.
A representative for Khanna, a California Democrat who is an outspoken progressive, said the confrontation occurred Wednesday in the middle of a three-day tour of the West Bank. As the congressman visited a Palestinian village that had been abandoned after settler attacks, masked men with guns stopped his group and refused to let them leave.
The New York Times said the incident was witnessed by one of its photographers. Khanna's office said it occurred in the town of Khirbet Zanuta.
Khanna said that when Israeli soldiers arrived he was dispirited to see them interact in a friendly manner with their captors and also block the exit for the congressman's party. Not until the U.S. Embassy and Israeli police were called was Khanna's group allowed to proceed.
"If this can happen to an American member of Congress, imagine what life is like for Palestinians who have no smartphones, no security, and no national platform," Khanna, who is exploring a presidential bid in 2028, said in a fundraising email he sent out shortly after his post Saturday about the incident.
In a statement, the IDF said it received a report of Israeli citizens blocking foreign nationals and media in Khirbet Zanuta.
"Upon receiving the report, IDF troops were dispatched to the scene, quickly dispersed the Israeli civilians, and reopened the blocked road," the military said in a statement. "The IDF soldiers operating in the area did not take part in blocking the road."
Democratic politicians from the United States have stepped up their criticism of Israel amid a sharp turn against the country by the party's voters. This week, former Chicago Mayor Rahm Emanuel, whose father was born in Jerusalem and fought in Israel's war of independence, gave a blistering speech last week in Tel Aviv in which he said Israel has become a "territorial pariah." Emanuel also is a potential White House contender.
In a recent survey by The Associated Press-NORC Center for Public Affairs Research, about 58% of Democrats said the U.S. is "too supportive" of Israelis.
Also Saturday, the Israeli military said it detained four suspects who were attacking foreign journalists traveling to Sinjil, another West Bank community. The assailants blocked the journalists' vehicle and damaged it and were armed with clubs and knives, according to the military's statement.
CNN reported that it had a team among the journalists who were attacked. The network said the journalists were there to cover the one-year anniversary of the killing of a Palestinian-American man who was beaten to death by Israeli settlers.
CNN's Oren Liebermann and KGO-TV / ABC7 Eyewitness News in San Francisco contributed to this story.