The voices of thousands of people rang nationwide on Saturday as protesters urged the reunification of hundreds of children separated from their parents at the U.S.-Mexico border.

Protesters chanted “shut detention down!” as they marched in New York City’s Foley Square while in El Paso, Texas, hundreds marched toward the Paso Del Norte (Santa Fe) Bridge that crosses into Juarez, Mexico.

In all, more than 600 events were planned across the country.

“We’re here because there are parents out there who can’t sing lullabies to their kids, so we’re going to sing on their behalf until they can sing together,” Tony-winning actor Lin-Manuel Miranda, who created the musical "Hamilton," told a crowd in the nation’s capital. He sang a lullaby dedicated to parents who are unable to sing to their children.

From immigrant-friendly cities like New York City and Los Angeles to conservative Appalachia and Wyoming, protesters are rallying under the Families Belong Together banner, pushing against President Trump’s controversial "zero tolerance" policy, under which some 2,000 families have been separated after crossing into the U.S. illegally from Mexico.

Across the country thousands waved signs: "I care, do you?" some read, referencing a jacket the first lady wore when visiting child migrants amid the global furor over the administration's zero-tolerance policy that forced the separation of more than 2,000 children from their parents. Her jacket had "I really don't care, do U?" scrawled across the back, and that message has become a rallying cry for Saturday's protesters.

According to The Associated Press, a strong turnout in Los Angeles, saw thousands of protesters gather downtown. Singer John Legend serenaded the crowd, AP said, while Democratic politicians who have clashed with Trump spoke against separating families at the U.S.-Mexico border.

Legend's wife, Chrissy Teigen, shared a photo from the rally on Instagram captioned, "baby's first rally. #keepfamiliestogether."

The couple have been outspoken opponents of Trump's administration.

Among the lawmakers, U.S. Rep. Maxine Waters called for impeachment, while Sen. Kamala Harris pointed to how migrant children taken from their parents will suffer lifelong trauma.

On the other side of the country, meanwhile, a rally outside City Hall in Portland, Maine, grew so large that police had to shut down part of a street as about 2,000 people chanted, cheered and prayed, the wire service said Saturday evening.

In Dallas, the protest was also largely peaceful. But police told AP five people were arrested outside an Immigration and Customs Enforcement building. According to AP, news station KXAS-TV reported that dozens of people were protesting outside the ICE building Saturday. Police said protesters began to block lanes of a service road. A police supervisor said five people were arrested when they refused police orders to move.

In a flurry of tweets on Saturday afternoon, President Trump, who was headed to his golf club in Bedminster, N.J., this weekend, addressed immigration in broad strokes, re-emphasizing his calls for strong border protections.

"When people come into our Country illegally, we must IMMEDIATELY escort them back out without going through years of legal maneuvering," the president said. "Our laws are the dumbest anywhere in the world. Republicans want Strong Borders and no Crime. Dems want Open Borders and are weak on Crime."

Some protesters also showed up near the New Jersey golf resort, waiving signs reading, "Do you know where our children are?" and "Even the Trump family belongs together."

Back in Washington, D.C., a woman only identified as Jocelyn took issue with how immigration and family separation are being handled. She said she and her son had spent nine months apart.

"During that time I was told that he could be put up for adoption," she said through a translator. "I was terrified that I might never see him again."

Smaller groups came together in city parks and downtown squares in every state, a total of 703 places across the country, 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.

Children joined in. A little girl in Washington, D.C., carried a handwritten sign: "I get my mommy. Why can't she?"

Dallas protest organizer Michelle Wentz says opposition to the policy has seemed to cross political party lines. She called it a "barbaric and inhumane" policy.

The protests come after several weeks of demonstrations across the country – many outside detention centers nationwide.

Tyler Houlton, a spokesman for the U.S. Department of Homeland Security, welcomed interest in the immigration system, saying 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 SLAPS DOWN DEMOCRATS' 'ABOLISH ICE' PUSH: 'IT WILL NEVER HAPPEN'

In tweets earlier in the day, Trump took to Twitter to approach the immigration furor from a different direction. He stressed his support for Immigration and Customs Enforcement amid calls from some Democrats for major changes to immigration enforcement.

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."

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.

Fox News' Elizabeth Zwirz, Jeffrey Rubin and The Associated Press contributed to this report.