Activists, parents and first-time protesters motivated by accounts of children separated from their parents at the U.S.-Mexico border are rallying in cities and towns across North America today to protest the Trump administration's immigration policies, calling for an end to the detention of immigrant families.

More than 700 planned marches drew hundreds of thousands of people across the country, from immigrant-friendly cities like New York and Los Angeles to conservative Appalachia and Indiana to the front lawn of a Border Patrol station in McAllen, Texas, near a detention centre where migrant children were being held in cages.

There, people held American and Texas flags and signs depicting a migrant father, mother and child as the Holy Family with haloed heads travelling through the desert.

Thousands dressed in white and gathered on Lafayette Square in Washington, across from the White House, with crowds chanting "Shame! Shame! Shame!" as speakers denounced the separation of children from their parents after they cross the U.S. border.

Activists shout during the rally to protest the Trump administration's immigration policies in New York on Saturday, June 30. (Kevin Hagen/Associated Press)

Protesters waved signs in English and Spanish, bearing slogans like "Where are the children?" and "Melania & Ivanka, stop the child abuse."

"The way they treat families, the way they treat immigrants — that's not America," protester Aneice Germain said of Donald Trump's tough stance on immigration, a cornerstone of his 2016 election campaign and his presidency.

Trump says illegal immigration fosters crime and he implemented a "zero tolerance" policy in May to prosecute all immigrants apprehended for entering illegally. That led to the separation of more than 2,000 children from their parents, causing an outcry this month, even from some allies of the Republican president.

U.S. President Donald Trump signed an executive order to stop the separation of illegal migrant children from their parents this week, but more than 2,000 children remain in detention, some thousands of kilometres from their families. Our U.S. political panel discusses the latest developments. 11:39

In a rare retreat on an issue that fires up his conservative base, Trump on June 20 ordered officials to detain families together.

A federal judge has ordered families be reunited and the administration asked the military to house immigrant families, leading the Pentagon to mull the construction of soft-sided camp facilities.

'What if it was your child?'

At the march in New York City, protesters chanted and sang as they gathered in sweltering heat at a Manhattan park before heading across the Brooklyn Bridge.

"It's important for this administration to know that these policies that rip apart families — that treat people as less than human, like they're vermin — are not the way of God, they are not the law of love," said the Rev. Julie Hoplamazian, an Episcopal priest marching in Brooklyn, whose own grandparents fled to the U.S. during the Armenian genocide.

"Jesus was a refugee," she said.

The protests drew several big names, including in L.A., where the assembled crowd was treated to a performance by singer John Legend. Some in the crowd spoke about how U.S. immigration policy has affected their own families.

John Legend, Laverne Cox among those expected at <a href="https://twitter.com/hashtag/FamiliesBelongTogetherLA?src=hash&ref_src=twsrc%5Etfw">#FamiliesBelongTogetherLA</a> .Others have personal reasons for being at rally. US-born Natalie Mier says she was separated from her own family when her father was deported several yrs ago.She told me the pain doesn’t go away <a href="https://twitter.com/CBCNews?ref_src=twsrc%5Etfw">@CBCNews</a> <a href="https://t.co/fcxqRScYcs">pic.twitter.com/fcxqRScYcs</a> —@ZulekhaNathoo

Smaller groups came together in city parks and downtown squares in every state, and photos quickly started ricocheting around social media.

Some carried tiny white onesies. "What if it was your child?" was written on one. "No family jails," said another.

Among the targets of their censure: Trump, Attorney General Jeff Sessions and the agencies Immigration and Customs Enforcement and Customs and Border Protection. Protesters were due to march on the Justice Department building in Washington later in the afternoon.

Crowds also gathered in downtown Albuquerque, New Mexico, with protesters voicing concerns about everything from abortion rights and the future makeup of the U.S. Supreme Court, to what, if any, influence Russia might have on American politics.

'We are here to resist'

Local resident Margarita Perez held up a small Mexican flag as speakers addressed the crowd. Accompanied by her daughter, she said she was concerned about the children who were being detained and for those parents who did not know where their children were taken.

Albuquerque Mayor Tim Keller, a Democrat, told the crowd of his trip to the U.S.-Mexico border, where he said he and other mayors were denied a tour of a shelter at the Tornillo port of entry outside of El Paso, Texas.

He elicited a roar from the crowd when he said "We are here to push back, to resist."

A demonstrator participates in a Keep Families Together march in Manhattan on Saturday to protest against the Trump administration's immigration policy. (Shannon Stapleton/Reuters)

A protest was also held in Bedminster, N.J., where Trump is spending the weekend at a private golf course he owns in the community.

More than a dozen rallies were also organized in Canada, in cities that include Halifax, Ottawa, Toronto, Winnipeg, Vancouver and Edmonton.

In Toronto, a few hundred people gathered in front of the U.S. consulate, many bringing stuffed animals with them to represent the migrant children separated from their parents.

"Children are the real victims here, and they're helpless," said Luis Segura, who came to Canada from El Salvador when he was nine years old. "I couldn't imagine my son being taken from me, in a cage, and him trying to figure that out."

Though many who were expected to show up at the U.S. rallies were seasoned anti-Trump demonstrators, others were new to immigration activism, including parents who say they feel compelled to show up after heart-wrenching accounts of children forcibly taken from their families as they crossed the border illegally. In Portland, Ore., for example, several stay-at-home moms organized their first rally while caring for young kids.

We just kept hearing over and over again, if it was my child, I would want someone to do something. - Jess Morales Rocketto of the National Domestic Workers Alliance

"I'm not a radical, and I'm not an activist," said Kate Sharaf, a Portland co-organizer. "I just reached a point where I felt I had to do more."

Immigrant advocacy groups say they're thrilled — and surprised — to see the issue gaining traction among those not tied to immigration.

"Honestly, I am blown away. I have literally never seen Americans show up for immigrants like this," said Jess Morales Rocketto, political director at the National Domestic Workers Alliance, which represents nannies, housekeepers and caregivers, many of whom are immigrants.

"We just kept hearing over and over again: If it was my child, I would want someone to do something."

Drawing on networks from women's marches

Saturday's rallies are getting funding and support from the American Civil Liberties Union, MoveOn.org, the National Domestic Workers Alliance and The Leadership Conference. But local organizers are shouldering on-the-ground planning, many of them women relying on informal networks established during worldwide women's marches on Trump's inauguration and its anniversary.

Tyler Houlton, a spokesperson for the U.S. Department of Homeland Security, welcomed interest in the immigration system and said only Congress has the power to change the law.

"We appreciate that these individuals have expressed an interest in and concern with the critical issue of securing our nation's borders and enforcing our immigration laws," Houlton said. "As we have indicated before, the department is disappointed and frustrated by our nation's disastrous immigration laws and supports action."

Trump took to Twitter on Saturday morning to show his support for Immigration and Customs Enforcement amid calls from some Democrats for major changes to immigration enforcement.

To the great and brave men and women of ICE, do not worry or lose your spirit. You are doing a fantastic job of keeping us safe by eradicating the worst criminal elements. So brave! The radical left Dems want you out. Next it will be all police. Zero chance, It will never happen! —@realDonaldTrump

Tweeting from New Jersey, Trump said that Democrats "are making a strong push to abolish ICE, one of the smartest, toughest and most spirited law enforcement groups of men and women that I have ever seen."

He urged ICE agents to "not worry or lose your spirit."

In Portland, Sharaf and other mothers who organized the rally hope to attract 5,000 people.

Right-wing activists with the group Patriot Prayer also had a permit to march later on Saturday and the Portland Police Bureau said Friday there would be a heavy police presence.

Sarah Jackson is the founder of Casa de Paz, an organization that helps detained immigrants find their families. Migrant parents separated from their children are struggling to navigate through the system with little to no help, she says, because the system is not equipped to handle this amount of people all at once. 5:53

Immigration attorney Linda Rivas said groups have met with U.S. authorities, congressional representatives and other leaders to discuss an escalating immigration crackdown that they say began decades ago. But the family separation policy has been a watershed for attracting a broader spectrum of demonstrators, she said.

"To finally have people on board wanting to take action, marching, taking to the streets, it's been motivating for us as advocates because we have to keep going," Rivas said.​