WASHINGTON - About 600 protesters, mostly women, on Thursday were detained by police for a mass sit-in against US President Donald Trump's "zero tolerance" immigration policy at the US Senate.

"I was just arrested with 500+ women and @WomensMarch to say @RealDonaldTrump's cruel zero-tolerance policy will not continue. Not in our country. Not in our name," Congresswoman Pramila Jayapal, a Democrat, tweeted.

"June 30 we're putting ourselves in the street again," she said, referring to the upcoming nationwide demonstrations over Trump's immigration policy scheduled for Saturday.

Thursday's sit-in was part of the #WomenDisobey protest, said organizers.

Local media said US Capitol Police arrested 575 people and charged them with unlawfully demonstrating. Protest organizers estimated the number was around 650.

Under Trump's "zero tolerance" policy, more than 2,000 children were separated from families who entered the United States illegally, sparking outrage home and abroad.